# Undefined function or variable

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aklapaz on 20 Mar 2017
Commented: aklapaz on 21 Mar 2017
Hello, I am new to Matlab and been trying to solve the below task: Write a function called light_speed that takes as input a row vector of distances in kilometers and returns two row vectors of the same length. Each element of the first output argument is the time in minutes that light would take to travel the distance specified by the corresponding element of the input vector. To check your math, it takes a little more than 8 minutes for sunlight to reach Earth which is 150 million kilometers away. The second output contains the input distances converted to miles. Assume that the speed of light is 300,000 km/s and that one mile equals 1.609 km.
So my function looks like that:
function [ Time,DistM ] = light_speed(A)
[~,n]=size(A);
Time = A(1,1:n).*(1000/18000000);
DistM = A(1,1:n).*0.621371192 ; end
However Matlab comes with this message: >> edit light_speed
>> M=[1 2 3] M = 1 2 3
>> light_speed(M)
Undefined function or variable 'light_speed'.
Why it can't recognize the function at all even though I have saved it?
Thanks

Beder on 20 Mar 2017
Did you save light_speed in the same .m file as the one that you're calling from?
a Code like the one below should work. Is your code structured like this?
a=1
b=myfunction(a)
function x=myfunction(a)
x=a+1;
end
aklapaz on 21 Mar 2017
Thank you.I had to save it again. How do we specify a vector with the size function? Is my solution correct? [~,n]=size(A);

You need to make sure it is on your path
or use the ribbon on the MAtlab GUI or just save it in your working directory.