Matlab M-File

Consider the following vector V=[10,4,7,-8,-3,-12] Write an m file in MATLAB that doubles the elements that are negative and are divisible by 2 and/or 4, and raise to the power of 2 the elements that are positive but greater than 6.

My solution is as above, however I have not managed to run it yet...

function V(i)=[10,4,7,-8,-3,-12];
for i=1:1:6;
if [V(i)<0 | mod(V(i),2)==0 | mod(V(i),4)==0],
    V(i)=V(i)*2;
end
if [V(i)>0 & V(i)>6],
    V(i)=i*i;
end
V(i);

I kindly request your help. Thank you...

Answer 1

[James Tursa]

You should review the documentation on how to write a function, since your above code is not a correctly written function. First, come up with a name for your function, e.g. myFunction. Then create a new file called myFunction.m somewhere on the MATLAB path (e.g. your working directory). Then in that file put your code. E.g.,

function result = myFunction(V)
result = V;  % <-- allocate the result variable, copying all elements
%
% Insert your code here to create the result variable from the V variable
%
return
end

I will give you some hints about correcting your code:

Change this loop:

for i=1:1:6;  % <-- hard coded for exactly 6 elements

to this

for i=1:numel(V)  % <-- allows any size input

The following test has an error in the logic (compare this carefully with the requirement):

if [V(i)<0 | mod(V(i),2)==0 | mod(V(i),4)==0]

The following line has an error on the right hand side calculation (compare this carefully with the requirement):

    V(i)=i*i;

If you don't see what the errors are, step through a small example by hand and compare that to the code result. E.g., at the command line type this:

V=[10,4,7,-8,-3,-12];
myFunction(V)