Compare digits of 2 strings

Looking to compare a string of pi to a calculated string to check for digit similarity between the two (ie 3.1415 compared to 3.1426, 3 digits accurate)

The idea is to put it into a table that can be read as 3 columns with "n values", "calculated values", "digit accuracy".

my issue is i dont know how to look at each character of the strings to compare, as when i try to get the 1st digit it responds with the whole string.

Example code:

clear; format longg;
calcPi=zeros(1, 4); digitAccuracy=zeros(1,4); 
nrange=[1*10^2, 1*10^4, 1*10^6]; step=1;
piString=sprintf("%.14f", pi);%convert pi to a string with 14 decimals

for n=nrange 
    k=1:n;
    sumEQ=sum(1./k.^2); %find (pi^2)/6
    calcPi(step)=sqrt(6*(sumEQ)); %solve for pi
    
    calcString=sprintf("%.14f",calcPi(step));%convert calcPi to string with 14 decimals
    
    for i = 1:strlength(calcString) %loop for every digit of calcString
        calcDigit=str2double(calcString(i)); %take i'th digit of calcString
        piDigit=str2double(piString(i)); %take i'th digit of piString
        
        if calcDigit == piDigit %are both i'th digits equal?
        digitAccuracy(step) = 1+digitAccuracy(step); %if yes, increase counter by 1
        end 
        
    end
    step=step+1; %step increase for array indexing
end

[Taiga]

update: using num2str instead of sprintf works, however on 2nd loop of the for statement, error "index exceeds number of array elements" occurs

Answer 1

[Tien]

Your calcString and piString are of string type. I believe you have to convert those strings to character vectors for the loop to work correctly. Simply change the double quote to single quote in the sprintf lines would do the trick:

piString=sprintf('%.14f', pi);

calcString=sprintf('%.14f',calcPi(step));

[Taiga]

this worked perfectly, thanks! wasnt aware " and ' had specific differences

[Stephen23]

"wasnt aware " and ' had specific differences"

Completely different:

• ' defines a character array, each element is exactly one character.
• " defines a string scalar, each element is a container containing arbitrarily long text

This is explained in the documentation:

https://www.mathworks.com/help/matlab/characters-and-strings.html