How to formulate the following conditional function?

Consider the following function,f:

if x=0:

f(x)=0

else:

f(x)=sin(1/x)

how to formulate that as a Matlab M-File function?

thanks?

[Geoff Hayes]

moh - you state that f is a function but perhaps it is an array instead? are you passing in x to this function and expect to get something returned? Is x an integer or real number? Please provide more details.

[moh pouladin]

f is a function and x is a real number.

Answer 1

[Image Analyst]

This works:

function output = f(x)
output = sin(1 ./ x);
% Zero out any values where x is exactly zero.
output(x == 0) = 0;
% Note, this works regardless if x is a scalar or a vector or matrix.

To call it, here is an example:

x = randi(5, 6, 6) - 1
output = f(x)

[moh pouladin]

I cann't understand your answer.

Would you please give me the exact definition of f(x) in Matlab language, so I could copy and paste it to the Matlab M-file editor and check the output of the function.

Thanks.

[Image Analyst]

Attached is a script that works for scalar, vector, and matrix. Copy and paste into a script, like test.m, like I did with the attached.

clc;    % Clear the command window.
clearvars;
close all;  % Close all figures (except those of imtool.)
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;fontSize = 22;

% x is a scalar
x = 5
output = f(x)
% x is a vector
x = randi(5, 6, 6) - 1
output = f(x)
% x is a matrix
x = randi(5, 6, 6) - 1
output = f(x)

function output = f(x)
output = sin(1 ./ x);
% Zero out any values where x is negative
output(x == 0) = 0;
% Note, this works regardless if x is a scalar or a vector.
end

To integrate output, you could either sum up the values or use trapz() - whichever algorithm you want.

area = sum(output);
area = trapz(x, output);

[moh pouladin]

the key point in your script that I missed, is:

output(x == 0) = 0;

would you please suggest a book to read more about Matlab.

thanks

[Walter Roberson]

https://blogs.mathworks.com/steve/2008/01/28/logical-indexing/

https://www.mathworks.com/help/matlab/math/matrix-indexing.html#bq7egb6-1