Top PDF Linear Regression Using R: An Introduction to Data Modeling

Linear Regression Using R: An Introduction to Data Modeling

Linear Regression Using R: An Introduction to Data Modeling

4.2 || Identifying Potential Predictors The first step in developing the multi-factor regression model is to identify all possible predictors that we could include in the model. To the novice model developer, it may seem that we should include all factors available in the data as predictors, because more information is likely to be better than not enough information. However, a good regression model explains the relationship between a system’s inputs and output as simply as pos- sible. Thus, we should use the smallest number of predictors necessary to provide good predictions. Furthermore, using too many or redundant predictors builds the random noise in the data into the model. In this sit- uation, we obtain an over-fitted model that is very good at predicting the outputs from the specific input data set used to train the model. It does not accurately model the overall system’s response, though, and it will not appropriately predict the system output for a broader range of inputs than those on which it was trained. Redundant or unnecessary predictors also can lead to numerical instabilities when computing the coefficients.
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Lesson 8: Introduction to Databases E-R Data Modeling

Lesson 8: Introduction to Databases E-R Data Modeling

Translating all constraints may not be possible There may be instances in the translated schema that cannot correspond to any instance of R Exercise: add constraints to the relationships R A , R B and R C to ensure that a newly created entity corresponds to exactly one entity in each of entity sets A, B and C

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Using Baseball Data as a Gentle Introduction to Teaching Linear Regression

Using Baseball Data as a Gentle Introduction to Teaching Linear Regression

3. Multiple Linear Regression as a Tool to Explain Winning Percentage To improve the ability to “explain” the variation in the team’s winning percentage, the concept of multiple linear regression is introduced, where it is mentioned that adding new predictor variables can help to increase the R 2 term. That is, it is mentioned that one can do a better job of explaining the variation in the team’s winning per- centage. It is also emphasized that we must be frugal in adding predictor variables, as many predictor variables in a single model can make the model difficult to interpret. In the context of our baseball example, Payroll is removed and five new predictor variables are introduced. Table 2 shows the new data set.
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Using Baseball Data as a Gentle Introduction to Teaching Linear Regression

Using Baseball Data as a Gentle Introduction to Teaching Linear Regression

3. Multiple Linear Regression as a Tool to Explain Winning Percentage To improve the ability to “explain” the variation in the team’s winning percentage, the concept of multiple linear regression is introduced, where it is mentioned that adding new predictor variables can help to increase the R 2 term. That is, it is mentioned that one can do a better job of explaining the variation in the team’s winning per- centage. It is also emphasized that we must be frugal in adding predictor variables, as many predictor variables in a single model can make the model difficult to interpret. In the context of our baseball example, Payroll is removed and five new predictor variables are introduced. Table 2 shows the new data set.
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Introduction to Linear Regression

Introduction to Linear Regression

explained for these data is 12.96. How is this value divided between HSGPA and SAT? One approach that, as will be seen, does not work is to predict UGPA in separate simple regressions for HSGPA and SAT. As can be seen in Table 2, the sum of squares in these separate simple regressions is 12.64 for HSGPA and 9.75 for SAT. If we add these two sums of squares we get 22.39, a value much larger than the sum of squares explained of 12.96 in the multiple regression analysis. The explanation is that HSGPA and SAT are highly correlated (r = .78) and therefore much of the variance in UGPA is confounded between HSGPA or SAT. That is, it could be explained by either HSGPA or SAT and is counted twice if the sums of squares for HSGPA and SAT are simply added.
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Lecture 4: Introduction to Multiple Linear Regression

Lecture 4: Introduction to Multiple Linear Regression

4. The proportion of variation in the response explained by the regression model: R 2 = Model (or Regression) SS / Total SS never decreases when new predictors are added to a model. The R 2 for the simple linear regression was .076, whereas R 2 = .473 for the multiple regression model. Adding the weight variable to the model increases R 2 by 40%. That is, weight and fraction together explain 40% more of the variation in systolic blood pressure than explained by fraction alone. I am not showing you the output, but if you predict systolic blood pressure using only weight, the R 2 is .27; adding fraction to that model increases the R 2 once again to .47. How well two predictors work together is not predictable from how well each works alone.
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Modeling Of A Stereo Vision System Using A Genetic Algorithm Based Fuzzy Linear Regression.

Modeling Of A Stereo Vision System Using A Genetic Algorithm Based Fuzzy Linear Regression.

Keywords—Fuzzy Linear Regression, Genetic Algorithm, Stereo Vision, Range Finder, Factorial Design 1. Introduction Empirical data modeling is a common approach used by researchers to understand the relationship between input factors and output variables of a system under investigation. Traditionally the ordinary least- squares (OLS) regression method is used to approximate the true function of a system or process. The descriptive model is a crisp polynomial function, which can be applied only if the underlying statistical model assumptions are satisfied; e.g. the normality of error terms and the predicted value, and the equality of variances [1]. In many real world problems, the variables under consideration do not always distribute as stated in statistical properties and the systems tend to be complex. Violation of the assumptions implies an invalid model, which may not be able to precisely describe the investigated system.
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Chapter 13 Introduction to Linear Regression and Correlation Analysis

Chapter 13 Introduction to Linear Regression and Correlation Analysis

„ The sample correlation coefficient r is an estimate of ρ and is used to measure the strength of the linear relationship in the sample observations.. (continued)..[r]

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Using R for Linear Regression

Using R for Linear Regression

[1] 4 22 44 60 82 The expected model for the data is signal = β o + β 1 ×conc where β o is the theoretical y-intercept and β 1 is the theoretical slope. The goal of a linear regression is to find the best estimates for β o and β 1 by minimizing the residual error between the experimental and predicted signal. The final model is

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(Non) Linear Regression Modeling

(Non) Linear Regression Modeling

See [3] and [18] for more details on detection and treatment of ill-conditioned problems. The multicollinearity has important implications for LS. In the case of exact multicollinearity, matrix X ⊤ X does not have a full rank, hence the so- lution of the normal equations is not unique and the LS estimate b LS is not identified. One has to introduce additional restrictions to identify the LS esti- mate. On the other hand, even though near multicollinearity does not prevent the identification of LS, it negatively influences estimation results. Since both the estimate b LS and its variance are proportional to the inverse of X ⊤ X, which is nearly singular under multicollinearity, near multicollinearity inflates b LS , which may become unrealistically large, and variance V ar(b LS ). Conse- quently, the corresponding t-statistics are typically very low. Moreover, due to the large values of (X ⊤ X ) −1 , the least squares estimate b LS = (X ⊤ X ) −1 X ⊤ y reacts very sensitively to small changes in data. See [13] for a more detailed treatment and real-data examples of the effects of multicollinearity.
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Rainfall Runoff Modeling using Multiple Linear Regression Technique

Rainfall Runoff Modeling using Multiple Linear Regression Technique

Keywords: Rainfall, Runoff, Modeling, Multiple Linear Regression. I. INTRODUCTION Hydrological models are important and necessary tools for water and environmental resources management. Demands from society on the predictive capabilities of such models are becoming higher and higher, leading to the need of enhancing existing models and even of developing new theories. Existing hydrological models can be classified into three types, namely, 1) empirical models (black-box models); 2) conceptual models; and 3) physically based models. To address the question of how land use change and climate change affect hydrological (e.g. floods) and environmental (e.g. water quality) functioning, the model needs to contain an adequate description of the dominant physical processes. Following the blueprint proposed by Freeze and Harlan (1969), a number of distributed and physically based models have been developed, among which are the well-known SHE (Abbott et al., 1986a, b), MIKE SHE (Refsgaard and Storm, 1995), IHDM (Beven et al., 1987; Calver and Wood, 1995), and THALES (Grayson et al., 1992a) models. These models are able to produce variations in state-variables over space and time, and representations of internal flow processes. It is assumed that the parameter values in the equations of such models can be obtained from measurements as long as the models are used at the appropriate scale. Physically- based distributed models particularly aim at predicting the effects of land use change. However, considerable debate on both the advantages and disadvantages of such models has arisen along with research and applications of those models (see, e.g. Beven 1989, 1996a, b, 2002; Grayson et al., 1992b; Refsgaard et al., 1996; O’Connell and Todini, 1996). In general, such models are very data-intensive and time- consuming when applied in a fully distributed manner.
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An investigation into Functional Linear Regression Modeling

An investigation into Functional Linear Regression Modeling

In this chapter, the tools for converting high frequency observed data points to con- tinuous functions were discussed. If the observed points exhibit periodic features then the Fourier Basis functions are suited for smoothing the data. For non-periodic data, the B-Splines Basis functions are recommended to smooth the data. Other ba- sis functions such as Gaussian Basis and Haar Wavelets have the ability to fit both periodic and non-periodic data as long as an appropriate number of basis functions and the optimal smoothing parameter are determined. Three model selections were studied: Least Square method, Maximum Likelihood method and Penalized Maxi- mum Likelihood method. Once a model is selected, it needs to be evaluated. Four kinds of model criteria were discussed in that regard: Generalized Cross-Validation, Generalized Information Criteria, modified Akaike Information Criteria and Gener- alized Bayesian Information Criteria. The resulting functions mimicking the random trajectory of the observed data are the Functional Data. Functional descriptive statistics such as the Functional Mean, Functional Variance can be derived from the Functional Data. The last sections of this chapter touched on important aspects related to computating Functional Data. The use of parallel computing seems to be viable solution to the computationally intensive algorithms.
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Using Multivariable Linear Regression Technique for Modeling Productivity Construction in Iraq

Using Multivariable Linear Regression Technique for Modeling Productivity Construction in Iraq

9. Data Collection Researcher has identified that suitable method of data collection influenced the accuracy of the production rates values. However questionnaire survey is the most com- monly data collection method adopted by the researcher to collect information on factors and production There- fore, direct observation method has been selected for collecting the data in this research. Pilot study has been done by selecting ten construction projects in different parts of Iraq. Work sampling approach has been used to measure the production rates at site to calculate duration of activity on daily basis at specific time interval using stop watch. Researcher has been able to get fifteen (15) number of observation from each of ten (10) projects at
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ASSESSMENT OF LIQUEFACTION POTENTIAL OF SOIL USING MULTI-LINEAR REGRESSION MODELING

ASSESSMENT OF LIQUEFACTION POTENTIAL OF SOIL USING MULTI-LINEAR REGRESSION MODELING

1. INTRODUCTION Liquefaction had been studied extensively by researchers all around the world right after two main significant earthquakes in 1964. Since than a number of terminologies, conceptual understanding, procedures and liquefaction analysis methods have been proposed. A well-known example is the 1964 Niigata (Japan) and 1964 Great Alaskan Earthquake in which large scale soil liquefaction occurred, causing wide spread damage to building structures and underground facilities [1]. Development of liquefaction evaluation started when Seed and Idriss (1971) [2] published a methodology based on empirical work termed as “simplified procedure”. It is a globally recognized standard which has been modified and improved through Seed (1979) [3], Seed and Idriss (1982) [4], Seed et al. (1985)[5] ,National Research Council (1985) [6], Youd and Idriss(1997) [7], Youd et al. (2001) [8]; Idriss and Boulanger(2006) [9]. Liquefaction of loose, cohesionless, saturated soil deposit is a subject of intensive research in the field of Geo-technical engineering over the past 40 years. The evaluation of soil liquefaction phenomena and related ground failures associated with earthquake are one of the important aspects in geotechnical engineering practice. It will not only cause the failure on superstructure, but also the substructure instability and both lead to catastrophic impact and severe casualties. For urban cities with alarmingly high population, it becomes necessary to develop infrastructural facilities with several high rise constructions. It is one of the primary challenge for Civil Engineers to provide safe and economical design for structures, particularly in earthquake prone areas. The in situ data are used to estimate the potential for “triggering” or initiation of seismically induced liquefaction. In the context of the analyses of in situ data, the assessment of liquefaction potential are broadly classified as:
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An introduction to hierarchical linear modeling

An introduction to hierarchical linear modeling

Hofmann, 1997). HLM is prevalent across many domains, and is frequently used in the education, health, social work, and business sectors. Because development of this statistical method occurred simultaneously across many fields, it has come to be known by several names, including multilevel - , mixed level-, mixed linear-, mixed effects-, random effects-, random coefficient (regression)-, and (complex) covariance components-modeling (Raudenbush & Bryk, 2002). These labels all describe the same advanced regression technique that is HLM. HLM simultaneously investigates relationships within and between hierarchical levels of grouped data, thereby making it more efficient at accounting for variance among variables at different levels than other existing analyses.
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Regression Modeling Of Data Collected Using Respondentdriven Sampling

Regression Modeling Of Data Collected Using Respondentdriven Sampling

The modeler’s first step in identifying underlying network structure is to assess whether or not the sample has mixed across geographic area and interview sites. If the underlying network is geographically integrated, we would expect to see geographic area (and site of interview) randomly distributed within and across recruitment trees. If the underlying network is completely segregated, we would expect no mixing across geographic areas such that all members of a recruitment tree would be interviewed in the same area (or at the same site). 7 There are a few approaches available to assess geographic and site mixing; the most preferable is examination of homophily using the standard RDS estimation approach (homophily is the tendency to associate with those similar to oneself). 8 If geographic area homophily is high, the modeler will need to consider including geography as a factor in his/her regression model. If there is more than one site in any geographic area, the modeler should examine homophily by site to make sure that the sample is not segregated by site within area (i.e., to make sure the network is truly structured by geographic area and not at some finer level). If there is not mixing across sites, the sample should be divided into multiple samples for population estimation (as in Heckathorn 1997), which will avoid the problems posed by the giant-component assumption. Additionally, the modeler should consider estimating a fixed-effects model on geographic area, interview site, or recruitment tree as a regression strategy if he/she believes that between-cluster variation at any of these levels is correlated with a model’s independent variables.
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A joint regression modeling framework for analyzing bivariate binary data in R

A joint regression modeling framework for analyzing bivariate binary data in R

The effects of bmi , income , age and education in the treatment and outcome equations show different de- grees of non-linearity. The point-wise confidence intervals of the smooth functions for bmi in the treatment and outcome equations contain the zero line for the whole range of the covariate values. The intervals of the smooth for income in the outcome equation contain the zero line for most of the covariate value range. This suggests that bmi is a weak predictor of private health insurance and health care utilization, and that income might not be a very important determinant of hospital utilization. Similar conclusions can be drawn by look- ing at the p-values reported in the summary output. As for the remaining variables, the estimated effects have the expected patterns. For example, age is a significant determinant in both equations. The probability of purchasing a private health insurance is found to increase with age . The likelihood of using health care services also increases with age . Insurance decision as well as health care utilization appear to be highly asso- ciated with education . Education is likely to increase individuals’ awareness of health care services and the benefits of purchasing a private health insurance. Higher household income is associated with an increased propensity of purchasing a private health insurance. See for example [7] for further details.
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Fitting Models to Biological Data using Linear and Nonlinear Regression

Fitting Models to Biological Data using Linear and Nonlinear Regression

Tip: Scatchard, Lineweaver-Burk, and related plots are outdated. Don’t use them to analyze data. The problem with these methods is that they cause some assumptions of linear regression to be violated. For example, transformation distorts the experimental error. Linear regression assumes that the scatter of points around the line follows a Gaussian distribution and that the standard deviation is the same at every value of X. These assumptions are rarely true after transforming data. Furthermore, some transformations alter the relationship between X and Y. For example, when you create a Scatchard plot the measured value of Bound winds up on both the X axis(which plots Bound) and the Y axis (which plots Bound/Free). This grossly violates the assumption of linear regression that all uncertainty is in Y, while X is known precisely. It doesn't make sense to minimize the sum-of-squares of the vertical distances of points from the line if the same experimental error appears in both X and Y directions.
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Load Estimation and Prediction on Passport Data          Using Linear Regression

Load Estimation and Prediction on Passport Data Using Linear Regression

Understanding various trends and predicting these trends in advance in passport systems help to know the various aspects of the nation’s growth and development and thereby focussing on the areas of the population which are either blooming or need more attention, Industry analysis across fast moving consumer goods and services, including market performance, market size, company and brand shares and profiles of leading companies and brands; data and analysis on consumer lifestyles, population trends, and socioeconomic analysis for every country, lifestyle and consumer type down to the city level; timely commentary on factors influencing the global, regional and local business environment; surveys exploring consumer opinions, attitudes and behaviors. The most important part discussed in the given project is to estimate or predict the load or the number of passports that can be issued in coming few years based on the number of passports already being issued in last few years. This analysis thus can help the authorities in predicting the nation’s development in coming years.
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Consistent Estimation of Linear Regression Models Using Matched Data

Consistent Estimation of Linear Regression Models Using Matched Data

16 March 2017 Abstract Economists often use matched samples, especially when dealing with earn- ings data where a number of missing observations need to be imputed. In this paper, we demonstrate that the ordinary least squares estimator of the linear regression model using matched samples is inconsistent and has a non- standard convergence rate to its probability limit. If only a few variables are used to impute the missing data, then it is possible to correct for the bias. We propose two semiparametric bias-corrected estimators and explore their asymp- totic properties. The estimators have an indirect-inference interpretation and they attain the parametric convergence rate if the number of matching vari- ables is no greater than three. Monte Carlo simulations confirm that the bias correction works very well in such cases.
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