MATLAB: How to assign a variable to a string

assignMATLABstringvariable

I have a mat file containing a table one column with numbers from 1 to 50, I just want to assign avariable to first column an than apply this:
tf = ismember(M, [7; 8; 9]);
idx = find(diff(tf)>0)+1+(0:12);
answer = reshape(M(idx).', [], 1)
If I put 
M = [1 2 3 4...49 50]
and then 
tf = ismember(M, [7; 8; 9]);
idx = find(diff(tf)>0)+1+(0:12);
answer = reshape(M(idx).', [], 1)
I have the correct results that display only the numbers after 9 but I want to exclude the M = [1 2 3 4…49 50] and to assign a variable to entire column because my numbers are always different except 7,8,9
I tried this 
M = T(:,:);
where T is the table from mat file but:
Error using table/ismember (line 27)
A and B must both be tables.
If I put directly:
 tf = ismember(X, [7; 8; 9]); %X is table from mat file
idx = find(diff(tf)>0)+1+(0:12);
vals = reshape(X(idx).', [], 1);
I get this error :
Error using +
Matrix dimensions must agree.
Thanks

Best Answer

>> whos -file simplu
  Name      Size            Bytes  Class    Attributes
  T          -               1440  table              
>> load simplu
>> whos T
  Name       Size            Bytes  Class    Attributes
  T         50x1              1440  table              
>> T(1:5,:)
ans =
  5×1 table
    Var1
    ____
    1.00
    2.00
    3.00
    4.00
    5.00
>> tf=ismember(T,[7:9]);
Error using tabular/ismember (line 37)
A and B must both be tables, or both be timetables. 
>> tf=ismember(T.Var1,[7:9]);
>>
Error is correct; T is a table and [7;8;9] is a vector of double...never the twain shall meet.
As the second shows, you need to reference the variable in the table.
ADDENDUM:
Error using tabular/ismember (line 37)
A and B must both be tables, or both be timetables.
The error message is correct, as far as it goes. It was written specifically for the case of the tabular/ismember function; what it neglects to point out is that both could be numeric and the alternate ismember method would work as well...
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