seach string in arraycell and find idx

C = {'A',31;
    'B',5;
    'C',3}

C = 3×2 cell array
    {'A'}    {[31]}
    {'B'}    {[ 5]}
    {'C'}    {[ 3]}

idx = find(ismember(C,{'A'}))

Error using cell/ismember
Input A of class cell and input B of class cell must be cell arrays of character vectors, unless one is a character vector.

Answer 1

[David Hill]

C = {'A',31;
    'B',5;
    'C',3};
idx = find(ismember(C(:,1),{'A'}))

idx = 1

Answer 2

[Dyuman Joshi]

When using ismember, if any of the input is a Cell array, it is expected that it will be a cell array of character vectors.

> which is what the error states

> which is mentioned in the documentation as well - Input Arguments for ismember()

But C is not a homogenueous cell array of character vectors, it has numeric data as well. So the above code does not work.

Use (the more robust) strcmp instead -

C = {'A',31;
    'B',5;
    'C',3}

C = 3×2 cell array
    {'A'}    {[31]}
    {'B'}    {[ 5]}
    {'C'}    {[ 3]}

%Comparing with cell array of character vector
idx = find(strcmp(C,{'A'}))

idx = 1

%Comparing with character
idx = find(strcmp(C,'A'))

idx = 1

%Comparing with string
idx = find(strcmp(C,"A"))

idx = 1