The lm tag has no wiki summary.
0
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1answer
40 views
Basic questions concerning the interpretation of results from summary(lm(…~…)) in R [duplicate]
set.seed(11)
a = runif (12)
b = rep(c(1,2,3),4)
summary(lm(a~b))$coeff
summary(lm(a~b-1))$coeff
What does a p.value for the intercept means ?
What differences ...
1
vote
1answer
60 views
Is this an error or not?
I am trying to fit a second order polynomial. I center and scale my predictors and fit the data using the lm function. I did ...
1
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2answers
166 views
Standardized residuals in R's lm output
I have a quick question: if I plot the diagnostic plots to an R regression, a couple of them have "Standardized Residuals" as their y-axis such as in this plot:
My question is this: what are the ...
1
vote
1answer
112 views
How does one define own intercept in regression model in R?
My case is that I have one continuous DV variable and two categorical IVs containing 11 and 12 different levels (YEAR & MONTH) form 1998 to 2008.
Until now I have experimented a lot with ...
2
votes
1answer
43 views
Explanation of a step in derivation of residuals for R lm diagnostic?
I'm reading Faraway's book (http://cran.r-project.org/doc/contrib/Faraway-PRA.pdf) to try to understand R's lm diagnostic plots. On page 72 of the book is this:
I have been trying to understand a ...
2
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1answer
80 views
Curvature terms and model selection
I am running a model selection analysis with a continuous dependent variable and a variety of continuous and categorical explanatory variables. For two of my continuous explanatory variables I am ...
0
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1answer
71 views
Weighting the response variable in an lm
I want to do a simple lm of y~x where I weight my response variable. This is because
the values of y are actually each in turn the value of a slope of another regression of y~year i.e. rates of ...
4
votes
2answers
260 views
Calculate F-statistic / p-value for subset of co-efficients in R
I'm wondering if there's an easy way of calculating an F-statistic / p-value for a subset of model coefficients. Particularly in R? I'm not sure what test would be needed to calculate this. For ...
3
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3answers
519 views
R: Calculating mean and standard error of mean for factors with lm() vs. direct calculation -edited
When dealing with data with factors R can be used to calculate the means for each group with the lm() function. This also gives the standard errors for the estimated means. But this standard error ...
2
votes
2answers
135 views
R lm simultaneous parameter tests
Using R, I'd like to test whether multiple parameters in a regression model are
equal to specific values (by default, are multiple parameters equal to 0).
For example, in this regression model:
...
-1
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1answer
61 views
Estimating values with which to replace NA [closed]
I have a data set that consists of several timeseries for which I want to calculate estimates within those timeseries to replace NA values. I am familiar with ddply() and lm() but I am having a bit ...
2
votes
1answer
177 views
How does anova.lm in R calculates “Sum Sq”?
I'm learning R and trying to understand how lm() handles factor variables & how to make sense of the ANOVA table. I'm fairly new to statistics, so please be ...
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0answers
72 views
Differences between visualization of correlation line fit and R^2
I have to figures below, generated using R`s lm function.
If you notice Figure A (above) has higher R^2 value than Figure B (below).
But visually, it is clearly that data in Figure B fits better with ...
3
votes
1answer
518 views
Adjusted R-squared in lm() in R - exact formula?
What is the exact formula used in R lm() for the Adjusted R-squared? How can I interpret it?
There seem to exist several formula's to calculate Adjusted R-squared.
Wherry’s formula ...
5
votes
2answers
229 views
lm() - model specification
If have multivariate data of 3 response variables and 2 factors (f1 and f2). I can specify an linear model in different ways for this data, however I don't know what the difference between the models ...
0
votes
1answer
72 views
lm regression in R - inconsistent R² for intercept-free model?
I am carrying a linear regression on some data. One of my variables is a factor (categorical). Using regression with an intercept leads to difficult interpretation, since one of the factor levels is ...
0
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0answers
153 views
Can dredge() in R package MuMIn deal with global model objects generated by gls() in nlme?
I am trying to use the function dredge() in the package MuMIn to compare AIC model-selection statistics for models of all ...
3
votes
2answers
99 views
Unable to figure out right transformation
I have obtained some data about how complexity of Java open source projects varies with time. I want to fit a curve to the data, however I am unable to figure out the right kind of transformation. I ...
9
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2answers
2k views
R: How is standard error of coefficients calculated in a regression?
I am interested in manually replicating for the purpose of my own understanding the calculation of the standard errors of estimated coefficients of the lm() ...
4
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3answers
252 views
Simple introduction to linear models in R
It was hard for me to understand linear models in R. There are a lot of documents for the case, but many of them are technical manuals rather than teaching the concept.
I found this article really ...
3
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3answers
1k views
Does lm() use partial correlation - R Squared Change?
I come from an SPSS background and am attempting to move to R for it's superior flexibility and data manipulation abilities. I have some concerns however as to ...
1
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0answers
328 views
Non-parametric alternative to linear regressions in R
I want to run series of simple lm in R, with a continuous/categorical outcome and binary group membership (patients - controls) and categorical predictors.
However the categorical predictor is ...
0
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0answers
59 views
Linear model overfit due to too many covariates? [duplicate]
Possible Duplicate:
Linear model overfitting due to too many covariates
My study design involves a control and 2 test groups plus some covariates.
Each group consists of around 20 ...
2
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1answer
144 views
Suggestion about morphometric analysis in R using lm or lme
Maybe this is an over-the-top question but I have many doubts regarding my recent analysis about deer skull measurements and how to proceed with the analysis. This is a sample of my dataset:
...
4
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1answer
523 views
Difference between CI of ANOVA level coefficients vs t-test CI - which one is “correct”?
How do I get the 95% confidence interval for ANOVA level coefficients? For comparison with a constant value, not multiple comparison (like MMC).
I tried to take the coefficient's SE from the model:
...
