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.
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