BennyMopps

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Hi, I'm having trouble setting up a procedure for an assignment, we're trying to find root mean square error and remove variable by variable to find the best line of fit etc etc... hopefully from the coding you can see what I'm am trying to do, but I don't understand why it is not working? I wonder if it has something to do with the X and Y being read in?
 
M:=readdata("C:\\Users\\bjense04.CSUMAIN.001\\Documents\\ass1Q2.txt",[float,float,float,float,float]):
convert(M,matrix):
with(LinearAlgebra):
n:=RowDimension(convert(M,matrix));
X:=convert(M[1..n,1..4],matrix):
Y:=convert(M[1..n,5..5],vector):
with(Statistics):
FullEQN:=LinearFit([1,a,b,c,d],X,Y,[a,b,c,d]);
#the next part is incomplete
rmse_mlr:=proc(Full)
local i, sq, n, predicted;
sq:=0:
for i from 1 to n do
 predicted:=subs([a=X[i,1],b=X[i,2],c=X[i,3],d=X[i,4]],Full);
 sq:=sq+(Y[i]-predicted)^2;
end do:
return sqrt(sq/n);
end proc;
 
 
I then test the procedure with 
rmse_mlr(FullEQN,X,Y);
 
and the response i get is

Error, (in rmse_mlr) final value in for loop must be numeric or character
 
help?
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