How to create an array using for loop?

Im trying to create an array B where the values are natural logs of A if greater than 1. If value is less or equal to 1 then I want 39 to be added to these values.

A=[8 14 3;-13 1 42;-39 -8 15];

B=zeros(size(A));

for k=1:size(A,1);

l=1:size(A,2);

if (A(k,l))>1

B(k,l)=log(A(k,l));

else

B(k,l)=A(k,l)+39 ;

end;

end;

I'm not sure where I'm going wrong. Can you please help me? Thanks

[per isakson]

Why do you think it goes wrong?

[Patrick]

Because the values should be the log of and all I get is just the sum of values A + 39.

Answer 1

[Walter Roberson]

You have

l=1:size(A,2);

so in the line

if (A(k,l))>1

you are doing a vector test, equivalent to

if A(k,:)>1

which is equivalent to

if A(k,[1 2 3])>1

When you test a vector in an "if" statement, the result is considered true only if all of the sub-results are considered true, just as if all() had been wrapped around the test, like

if all(A(k,:) > 1)

as some of your A entries do not satisfy that condition, the test is false and the else portion is executed.

[Patrick]

Sounds reasonable but how do I put >1 to make it actually work then?

[Image Analyst]

Instead of

l=1:size(A,2);

you'd have a for loop over l (bad variable name by the way):

for l = 1 : size(A, 2)

Answer 2

[Andrei Bobrov]

l = A > 1;
B = A;
B(l) = log(B(l));
B(~l) = B(~l) + 39;

[Jan]

Just to avoid confusions: The index is an lowercase "L", not a "1" (one).