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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