Unknown variable with str2num ?

%% Sir I am using a matlab code but I got a error here I am showing the main file only and error

function sigmaDloop(sb)
b=str2num(sb);
lmat=[1 20; 21 29; 30 36; 37 42; 43 47; 48 51; 52 55; 56 58; 59 61];
l1=lmat(b,1);
l2=lmat(b,2);
maxNumCompThreads(1);
T=70;
dimpP=20e-9;
dimpA=10e-9;
hbar=1.054571800e-34;   	
vf=1.1e6;  
kB=1.38064852e-23;	
nimp=5e14; %nimp= 5 x 10^10 cm^-2.
dspacer=9e-9;
nA=[0:1:20 22:2:100]; %in units of 10^10 cm^-2.
nP=nA;
EF=hbar*vf*sqrt(pi.*nA.*1e14);
TF=EF./kB;
mutildeA=Fmu(T./TF).*EF./(kB.*T);
mutildeP=mutildeA;
sigmadrag=zeros(length(mutildeP),length(mutildeA)); 
kB=1.38064852e-23;
hbar=1.054571800e-34;   
vf=1.1e6;   
dspacertilde=kB.*T.*dspacer./(hbar.*vf);
save(['sigmadragvals' num2str(b) '.mat'],'T','nA','nP','mutildeA','mutildeP','sigmadrag','dspacertilde','EF','TF');
for j=l1:l2
    for k=1:j
    diary(['sigmaDs' num2str(b) '.txt']);
    tic
    sigmadrag(j,k)=sigmaDtilde2d(dspacertilde,mutildeA(k),mutildeP(j)) 
    toc
    save(['sigmadragvals' num2str(b) '.mat'],'T','nA','nP','mutildeA','mutildeP','sigmadrag','dspacertilde','EF','TF','-append');
    diary off;
    end
end
end

%% and now error as

sigmaDloop

sb =

1

Error using str2num (line 32)

Requires string or character array input.

Error in sigmaDloop (line 7)

b=str2num(sb);

%% please give suggestion of this

[Stephen23]

The input sb is numeric, not a string or a character vector. Thus the error.

Answer 1

[KSSV]

Read about str2num. It takes string as input and conerts it to number. If the input is not string it will throw error like in your case.

str2num('2')    % no error '2' is string
str2num(2)     % error, 2 is number not a string      

In your case, your input sb is not a string.