nargin and the if statement
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Nicholas Salce
on 22 Sep 2016
Commented: Mukesh Mani
on 6 Jul 2023
Hi Im trying to understand how to use nargin but am having an issue. Hopefully someone can shed some light on. I copied this function from my text book
function z = sqrtfun(x,y)
if (nargin==1)
z = sqrt(x);
elseif (nargin==2)
z = sqrt(x+y);
end
Then in another script I have put together this code to call the function
clc;
clear;
close all;
x = input('x');
y = input('y');
z = sqrtfun(x,y);
fprintf('Answer z ::: %4.2f\n', z);
The issue i'm having is that if i leave y blank no value is displayed for z. If i enter a value for x and y i get an output value for z. I don't know why this happens??
0 Comments
Accepted Answer
Walter Roberson
on 22 Sep 2016
When you leave y blank in response to an input() prompt, what you get back is an empty array, and you provide that empty array as an argument. nargin tests the number of arguments passed, not what value they are, so it knows you are passing two arguments. This leads to the calculation
sqrt(x+y)
where x is not empty but y is empty. The sum of a non-empty array and an empty array is the empty array, so the result is empty.
You should modify your code to
function z = sqrtfun(x,y)
if (nargin==1) || isempty(y)
z = sqrt(x);
else
z = sqrt(x+y);
end
2 Comments
More Answers (1)
KSSV
on 22 Sep 2016
You change the function as follows:
function z = sqrtfun(x,varargin)
if (nargin==1)
z = sqrt(x);
elseif (nargin==2)
y = varargin{1} ;
z = sqrt(x+y);
end
When you enter one value i.e. x nargin = 1 then it goes to if, if you enter two values i.e x,y nargin will be 2. y will be stored in varargin and we are calling it in else statement.
2 Comments
Sultan Al-Hammadi
on 27 Nov 2018
what does nargin do?
and what is the functionality of "varargin{1}"?
Steven Lord
on 27 Nov 2018
See the description and examples on the nargin function documentation page for more information about what it does and how to use it.
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