Error with undefined operators

Hi guys,

I currently have this code to generate a spaghetti plot that shows the difference between two patient groups, where APPRDX_enrol = 1, and APPRDX_enrol = 2:

%t = readtable('PPMIMERGE_selectedcolumns2.csv');    Interestingly, if I uncomment this line, and comment the line below, it works fine
t = readtable('datasetfilteredVLTANIM.csv');

figure(1); 
%Parkinson's
SPAGLAB(t(t.APPRDX_enrol==1, :),    'Years_bl', 'VLTANIM', 'PATNO', '-r.');
%Controls
SPAGLAB(t(t.APPRDX_enrol==2, :),    'Years_bl', 'VLTANIM', 'PATNO', '-g.');

function h              = SPAGLAB(t, Years_bl, VLTANIM, PATNO, plot_format)

if nargin < 5
    plot_format         = '-b.';
end
subj_ids = t.PATNO;
uIds                    = unique(subj_ids);
n                       = length(uIds);
hold on;

for i = 1:n
    
    if isnumeric(subj_ids)
        
        index_i         = find(t.(PATNO) == uIds(i));
        
    else
        
        index_i         = find(strcmp(t.(PATNO),uIds{i}));
        
    end
    
    
    
    x_i                 = t.(Years_bl)(index_i);
    
    y_i                 = t.(VLTANIM)(index_i);
    
    
    
    h = plot(x_i, y_i, plot_format);
    title('Graph displaying VLTANIM scores for PD vs Control');
    xlabel('Years Since Baseline');
    ylabel('VLTANIM Score');
    
    
    
end

hold off;
end

I get this error:

Undefined operator '==' for input arguments of type 'cell'.

Any ideas?

[Guillaume]

Please give us the full text of the error message, everything in red, particulalry the bit that shows the line responsible for the error, so we don't have to guess.

Interestingly, if I uncomment this line, and comment the line below, it works fine

It's not particulalry surprising, you're importing two different files, there's no guarantee that they'll import the same way. Attaching an example of the two files would help.

[Barnaby Pickering]

Hi Guillaume,

I'll add in the full error message:

Warning: Column headers from the file were modified to make them valid MATLAB identifiers

before creating variable names for the table. The original column headers are saved in the

VariableDescriptions property.

Set 'PreserveVariableNames' to true to use the original column headers as table variable

names.

Undefined operator '==' for input arguments of type 'cell'.

Error in SPAGHETTIPLOT (line 10)

SPAGLAB(t(t.APPRDX_enrol==1, :), 'Years_bl', 'VLTANIM', 'PATNO', '-r.');

Unfortunately, I cannot add the full files, as they are patient data.

[Ioannis Andreou]

It might be, that

t.APPRDX_enrol = {1}

instead of

t.APPRDX_enrol = 1

. The error then appears because cells can not be compared with ==

Answer 1

[Guillaume]

The cause for the error is simple. In the file that doesn't work, at least one row of the APPRDX_enrol column contains non-numeric data. As a result, you end up with a cell array (probably of char vectors) instead of a column vector.

So, you either need to modify your code so it can cope with non-numeric data, but it's unclear what should be done in this case, or fix your import, it's hard to tell you what to do without an example file, or fix the file so the column only contains numeric data.

If the data in the files is confidential, it could be replaced by dummy data, as long as the format and numeric vs non-numeric is preserved.