Why it said that "Matrix index is out of range for deletion"

I already comine the string,it should not be a matrix anymore,but the commond window said "Matrix index is out of range for deletion".

first function is below:

function [strOut] = JoinName(strFirst, strLast)
Strin=strcat(strFirst,"_",strLast);
strOut= RemoveDash(Strin);
end

second function is below:

%Xuejian Sun,Lab7,11/12/2019
%write two function,the first is to determine whether string has dash and
%the second one is to remove dash
%clear windows,variables and figures

function [strOut]= RemoveDash(Strin)
Find=strfind(Strin,'-');
if isempty(Find)==1
    strOut=Strin;
else
    Strin(Find)=[];
    strOut=Strin;
end  

end

[Bhaskar R]

Can you provide input strings for the function JoinName used in the error case?

Answer 1

[Walter Roberson]

Strin=strcat(strFirst,"_",strLast);

Because you used "_" the result you get is going to be a string object, not a character vector.

Find=strfind(Strin,'-');

strfind() returns positions inside the scalar string object

    Strin(Find)=[];

Positions inside a scalar string object are not the same thing as indices into the string object. A scalar string object has index 1 only -- the index for a string object is which complete string you are accessing. Like ["hello", "bye"] has indices 1 for "hello" and 2 for "bye".

    Strin{1}(Find)=[];        %change the inside of the string