How to use varargin: to specify a second input variable with separate output

I am trying to make a function that converts an amount of liters (first input variable) into mililiters by default. Additionally, the function coverts liters into microliters and nanoliters if a second input 'micro' or 'nano' is specified.

I am stuck with the varargin part.

The convertion from liters into microliters seem to work, but when I try the input 'nano' i get the following error:

Matrix dimensions must agree.

In the line:

if varargin{1} == 'micro'

How to solve this problem???

function [converted_value] = convertLiters_sterre(liters, varargin)

%%CONVERTLITERS converts value in liters to milliliters, microliters or
%%nanoliters.

if nargin == 0
    error('No input');
elseif nargin == 1 && isnumeric(liters)
    
    converted_value = liters*1000;
    
elseif nargin > 1
    if varargin{1} == 'micro' 
        
        converted_value = liters*1000000;
        
    elseif varargin{1} == 'nano'
        
        converted_value = liters*1000000000;
        
    else
        error('Second input variable must be micro or nano');
    end 
else
    error('First input must be an integer or an array of numbers');
end

[Adam]

There may be other issues, but you should use

doc strcmp

to compare char arrays:

if strcmp( varargin{1}, 'micro' )

as a straight == will fail with the error you see if varargin{1} is not the same length as 'micro' and will still not give what you want even if they are the same length (you'll get a 5-element logical array)

Answer 1

[Jos (10584)]

You cannot compare strings with different lengths using ==. Use isequal or strcmpi instead, for instance:

if isequal(lower(varargin{1}), 'nano')
    % code here
end