Thanks for the replies everyone. Greatly appreciate it. Some progress, but
now I am getting the following values when I don't use "as.factor"
13.14167 25.11667 28.34167 49.14167 40.39167 66.86667
Is that what you guys get?
On Fri, Feb 12, 2010 at 5:00 PM, Phil Spector <spec...@stat.berkeley.edu>wrote:
> By converting the two variables to factors, you are fitting
> an entirely different model. Leave out the as.factor stuff
> and it will work exactly as you want it to.
>
> dat
>>
> V1 V2 V3 V4
> 1 s1 14 4 1
> 2 s2 23 4 2
> 3 s3 30 7 2
> 4 s4 50 7 4
> 5 s5 39 10 3
> 6 s6 67 10 6
>
>> names(dat) = c('id','y','x1','x2')
>> z = lm(y~x1+x2,dat)
>> predict(z)
>>
> 1 2 3 4 5 6 15.16667 24.66667
> 27.66667 46.66667 40.16667 68.66667
>
>
> - Phil Spector
> Statistical Computing Facility
> Department of Statistics
> UC Berkeley
> spec...@stat.berkeley.edu
>
>
>
> On Fri, 12 Feb 2010, Something Something wrote:
>
> Hello,
>>
>> I am trying to learn how to perform Multiple Regression Analysis in R. I
>> decided to take a simple example given in this PDF:
>> http://www.utdallas.edu/~herve/abdi-prc-pretty.pdf
>>
>> I created a small CSV called, students.csv that contains the following
>> data:
>>
>> s1 14 4 1
>> s2 23 4 2
>> s3 30 7 2
>> s4 50 7 4
>> s5 39 10 3
>> s6 67 10 6
>>
>> Col headers: Student id, Memory span(Y), age(X1), speech rate(X2)
>>
>> Now the expected results are:
>>
>> yHat[0]:15.166666666666668
>> yHat[1]:24.666666666666668
>> yHat[2]:27.666666666666664
>> yHat[3]:46.666666666666664
>> yHat[4]:40.166666666666664
>> yHat[5]:68.66666666666667
>>
>> This is based on the following equation (given in the PDF): Y = 1.67 + X1
>> +
>> 9.50 X2
>>
>> I ran the following commands in R:
>>
>> data = read.table("students.csv", head=F, as.is=T, na.string=".",
>> row.nam=NULL)
>> X1 = as.factor(data[[3]])
>> X2 = as.factor(data[[4]])
>> Y = data[[2]]
>> mod = lm(Y ~ X1*X2, na.action = na.exclude)
>> Y.hat = fitted(mod)
>> Y.hat
>>
>> This gives me the following output:
>>
>> Y.hat
>>>
>> 1 2 3 4 5 6
>> 14 23 30 50 39 67
>>
>> Obviously I am doing something wrong. Please help. Thanks.
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
[[alternative HTML version deleted]]
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
