Could someone please explain what is wrong in my function?

1 Ansicht (letzte 30 Tage)
I am attempting to create a fuction that takes in a matrix element and outputs with 1 0 or -1 depending on if th element is positive, zero or nagative respectively.
In the first line it underlines the first ( and , in the (A(r,c)) as well as both () around (r,c)
I am quite new so any help would be appreciated :)
function [Sign] = signum ( A(r,c) )
if A(r,c) == 0
Sign = 0;
elseif A(r,c) < 0
Sign = -1;
elseif A(r,c) > 0
Sign = 1;
end
disp(Sign);
end

Akzeptierte Antwort

Cris LaPierre
Cris LaPierre am 9 Jun. 2021
You have not defined r and c.
You have three options that I see.
  1. Pass in the single value to your function: Sign = signum (B)
  2. Pass in the entire matrix, and define r and c inside the function: Sign = signum (A)
  3. Pass in the matrix along with r and c: Sign = signum (A,r,c)
% Example of option 1
A = -5:5;
r = 1; c = 3;
B = A(r,c);
Sign = signum (B)
Sign = -1
function [Sign] = signum (B)
if B == 0
Sign = 0;
elseif B < 0
Sign = -1;
elseif B > 0
Sign = 1;
end
end
  2 Kommentare
Sergey Popov
Sergey Popov am 9 Jun. 2021
Thank you so much I was under the impression that you are able to pass a matrix in with custom r and c values using matrix indexing but i can see now why that doesnt work. I think option 3 works best in my case since my assigment requires that a specific matrix element is tested not the whole matrix.
Out of curiousty tho will passing the whole matrix in test every element in it one by one?
Cris LaPierre
Cris LaPierre am 9 Jun. 2021
The function will only do what you have coded it to do. Passing in an entire matrix will not automatically test every element. You would have to write you code in such a way that it tests every element.
You can call the function using A(r,c), but you can not declare your function input using that notation.
% Example of option 1
A = -5:5;
r = 1; c = 3;
Sign = signum (A(r,c))
Sign = -1
function [Sign] = signum (B)
if B == 0
Sign = 0;
elseif B < 0
Sign = -1;
elseif B > 0
Sign = 1;
end
end

Melden Sie sich an, um zu kommentieren.

Weitere Antworten (2)

David Hill
David Hill am 9 Jun. 2021
Why not just use built-in function sign()?
a=sign(A);
%then index into a for specific element
  1 Kommentar
Sergey Popov
Sergey Popov am 9 Jun. 2021
I am not allowed to use it cause my proffesor wanted us to develop a manual function for this operation.
I wish tho..

Melden Sie sich an, um zu kommentieren.


Jan
Jan am 9 Jun. 2021
function [Sign] = signum(A)
The indices (r,c) belongs to the caller of the function, not inside the function. You call this function by:
signum(A(r,c))

Kategorien

Mehr zu MATLAB finden Sie in Help Center und File Exchange

Produkte


Version

R2021a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by