Hi! Can you guys help mi with this code? The error is "Undefined function 'plus' for input arguments of type 'function_handle'."

clc; clear;
rect = @(n) rectangularPulse(-0.5,0.5,n);
sum  = 0;
for i=0:7
    a = @(n) (rect((n-19*i)/7));
    sum = sum + a;
    fplot(sum,[0,500]);
end

Answer 1

[Steven Lord]

You cannot add a function handle and a number or two function handles.

You can add the value returned by evaluating a function handle and a number.

fh1 = @(x) x.^2;
y = 1 + fh1(2) % works
y = 1 + fh1 % does not work

If you need a function handle as the output:

fh2 = @(x) x+1;
fh3 = @(x) sqrt(x);
fh4 = @(x) fh2(x) .* fh3(x)

This last is equivalent to:

fh4a = @(x) (x+1) .* sqrt(x)

[Felipe neut]

Thanks!! I solve the mistake. But now there is a new one:

FUN must be a function, a valid string expression, or an inline function object.

Error in fplot (line 60)
   fun = fcnchk(fun);

clc; clear;
rect = @(n) rectangularPulse(-0.5,0.5,n);
c = 0;
for i=0:7
    a = @(n) (rect((n-19*i)/7));
    c = c + a(i);
    fplot(c,[0,50]);
    hold on 
end

[Walter Roberson]

fplot() is to plot functions given their handle or symbolic expression. You are passing in a numeric scalar, c, instead.

for i=0:7
    a = @(n) (rect((n-19*i)/7));
    c(i+1) = a(i);
end 

plot(0:7, cumsum(c));

[Felipe neut]

Thanks a lot!!

Answer 2

[Geoff Hayes]

Felipe - the error message is due to the line

 sum = sum + a;

where you are trying to add a running total (named sum which is a poor choice of a local variable name since it conflicts with a MATLAB built-in function) with an anonymous function a

 a = @(n) (rect((n-19*i)/7));

So the error message makes sense. How should you be evaluating a? What should n be?

[Felipe neut]

Thanks for the answer! So what changes should I do to graph the function I attached? The function of the image is without the "DFT" Thanks!

[Geoff Hayes]

What should n be? Why have you chosen i to run from zero to seven?

[Felipe neut]

Oo sorry.. the problem is for l from 0 to 7, M=19, N=7. I have no more datas in the problem, and should achieve to this graph. Thanks again really :)