How the remove single apostrophe from a string?

yfunc=input('Enter any curve equation>') %If input yfunc= 'x^2', how to remove the apostrophe so that I can use the equation...

Answer 1

[Stephen23]

"how to remove the apostrophe so that I can use the equation..."

You can't, because a char array does not really have single quotes at the ends (unless you put them there), in just the same way the a numeric array does not contain any square brackets at the ends: the single quotes / square brackets are just the syntax that specifies how char arrays / numeric arrays are defined, but are not actually contained within the array itself. Let me demonstrate:

>> char(39) % single quote ASCII code
ans = '
>> double('hello') % get the ASCII codes for |hello|
ans =
   104   101   108   108   111

Can you see the code value 39 anywhere in that list?

In any case, if you have a char array then there is nothing that can be removed that will magically turn that char array into a function. A char array is just a collection of characters, which have no meaning other than any semantic meaning from how they were defined. If those characters happen to form a function in some variable then you will need to convert it into a function using str2func, I have shown you how below:

>> str = input('Enter function of x: ','s');
Enter function of x: x.^2+x
>> fun = str2func(sprintf('@(x)%s',str));
>> fun(0:10)
ans =
     0     2     6    12    20    30    42    56    72    90   110

Note that this will work as long as the function is entered using MATLAB syntax. If you want to define your own syntax then you will have to write a language parser using MATLAB, which is not a trivial task.

You really need to revise basic MATLAB types, such as what are char arrays and functions, because otherwise using MATLAB will not make sense:

https://www.mathworks.com/help/matlab/matlab_prog/fundamental-matlab-classes.html