Issues with tables and writetable from data passed from uitable

Hello, I have an array in a uitable that I want to save to a csv file as well as the column headings. It seems out of the write options available (writecell,writematrix, writetable) - it is only writetable that allows this

Writetable appears to work, but when I open the CSV file it hasn't and I can't understand why

This is my code:

T=app.UITable;           
data=T.Data;
C=array2table(data);   % Create table format
T.ColumnName
C.Properties.VariableNames=T.ColumnName;                     
C.Properties.Description='Scan Profile';
C = addprop(C,{'ScanStart','ScanTime'},{'table','table'});
C.Properties.CustomProperties.ScanStart = app.scannow;
C.Properties.CustomProperties.ScanTime = app.scantime;
C.Properties 
% C.Properties.VariableNames
writetable(C,savepath);
ReportMessage(app,'   Data Saved Using Writetable');

And in the command window I get this, indicating all is O.K

ans =

  6×1 cell array

    {'Idx'     }
    {'YPos(mm)'}
    {'Sep1'    }
    {'Sep2'    }
    {'<Sep>'   }
    {'dpixel'  }


ans = 

  TableProperties with properties:

             Description: 'Surface Profile'
                UserData: []
          DimensionNames: {'Row'  'Variables'}
           VariableNames: {'Idx'  'YPos(mm)'  'Sep1'  'Sep2'  '<Sep>'  'dpixel'}
    VariableDescriptions: {}
           VariableUnits: {}
      VariableContinuity: []
                RowNames: {}

   Custom Properties (access using t.Properties.CustomProperties.<name>):
               ScanStart: "29-Jan-2025 09:41:35"
                ScanTime: '174.2796'
                

But then the file looks like this:

So no headings.

And When i also try to load via readtable - all of the description and custom propeerrties are not present

                ans = 
                
                TableProperties with properties:
                
                Description: ''
                UserData: []
                DimensionNames: {'Row'  'Variables'}
                VariableNames: {'Var1'  'Var2'  'Var3'  'Var4'  'Var5'  'Var6'}
                VariableDescriptions: {}
                VariableUnits: {}
                VariableContinuity: []
                RowNames: {}
                CustomProperties: No custom properties are set.
                Use addprop and rmprop to modify CustomProperties.

Answer 1

[Cris LaPierre]

When I use your code, it saves a text file with headers.

T = uitable("Data",rand(10,6)*200);
T.ColumnName = {'Idx'  'YPos(mm)'  'Sep1'  'Sep2'  '<Sep>'  'dpixel'};

scannow = datetime('now');
scantime = 174.2796;

data=T.Data

data = 10×6

171.5249 59.8213 55.1595 9.8443 66.3039 91.6933 114.4676 199.7349 22.7675 4.9993 165.4376 100.5209 180.9859 6.9121 160.3118 4.1988 114.8329 172.3114 24.7842 77.0931 182.3518 40.8967 193.9196 157.5548 114.6593 20.5584 104.9205 134.5695 85.3426 13.2894 103.0309 146.9288 103.2514 67.8677 68.0959 190.1515 163.0010 113.4245 123.8324 124.5776 45.5248 8.1975 169.9012 72.2889 26.8094 98.0357 163.0888 77.1396 50.7894 157.4705 197.9429 110.9397 36.0781 35.7004 166.0988 97.1575 102.6416 161.2328 192.2395 56.0918

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C=array2table(data);   % Create table format
T.ColumnName

ans = 6x1 cell array
    {'Idx'     }
    {'YPos(mm)'}
    {'Sep1'    }
    {'Sep2'    }
    {'<Sep>'   }
    {'dpixel'  }

C.Properties.VariableNames=T.ColumnName;                     
C.Properties.Description='Scan Profile';
C = addprop(C,{'ScanStart','ScanTime'},{'table','table'});
C.Properties.CustomProperties.ScanStart = scannow;
C.Properties.CustomProperties.ScanTime = scantime;
C.Properties 

ans = 
  TableProperties with properties:

             Description: 'Scan Profile'
                UserData: []
          DimensionNames: {'Row'  'Variables'}
           VariableNames: {'Idx'  'YPos(mm)'  'Sep1'  'Sep2'  '<Sep>'  'dpixel'}
           VariableTypes: ["double"    "double"    "double"    "double"    "double"    "double"]
    VariableDescriptions: {}
           VariableUnits: {}
      VariableContinuity: []
                RowNames: {}

   Custom Properties (access using t.Properties.CustomProperties.<name>):
               ScanStart: 29-Jan-2025 13:33:11
                ScanTime: 174.2796

writetable(C);

However, only the text your see in the text file is saved, This means that most of the properties are lost when saving the data.

type('C.txt')

Idx,YPos(mm),Sep1,Sep2,<Sep>,dpixel
171.524925850556,59.8212564682293,55.1594713709911,9.84431199425133,66.3038601982844,91.6933173529022
114.467597476103,199.73486798322,22.7675124013326,4.99931215942839,165.437579063185,100.520894309323
180.985910692632,6.91213151523096,160.311776186681,4.19875762026298,114.832891340523,172.311408941264
24.7842180086756,77.0930680542322,182.351778449844,40.896744331036,193.919637971832,157.554847634127
114.659265530011,20.5583721104746,104.92049394351,134.569504533232,85.3425691967115,13.2894332691884
103.030871281363,146.928813035113,103.251375027387,67.8676920607874,68.0959064306495,190.151456549757
163.000970776348,113.424463285256,123.83239681839,124.577605791821,45.5247702437855,8.19750164544635
169.901197946299,72.2889152421108,26.8094140819827,98.0356640710453,163.0888367296,77.1395638567696
50.7893869535271,157.470487438356,197.942930322987,110.939718850646,36.0780921092393,35.700440729591
166.09876104556,97.1574559567013,102.641631726613,161.232808197506,192.239545789888,56.0917950510978

B = readtable('C.txt')

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 'VariableNamingRule' to 'preserve' to use the original column headers as table variable names.

B = 10x6 table
     Idx      YPos_mm_     Sep1      Sep2     x_Sep_    dpixel
    ______    ________    ______    ______    ______    ______

    171.52     59.821     55.159    9.8443    66.304    91.693
    114.47     199.73     22.768    4.9993    165.44    100.52
    180.99     6.9121     160.31    4.1988    114.83    172.31
    24.784     77.093     182.35    40.897    193.92    157.55
    114.66     20.558     104.92    134.57    85.343    13.289
    103.03     146.93     103.25    67.868    68.096    190.15
       163     113.42     123.83    124.58    45.525    8.1975
     169.9     72.289     26.809    98.036    163.09     77.14
    50.789     157.47     197.94    110.94    36.078      35.7
     166.1     97.157     102.64    161.23    192.24    56.092

B.Properties

ans = 
  TableProperties with properties:

             Description: ''
                UserData: []
          DimensionNames: {'Row'  'Variables'}
           VariableNames: {'Idx'  'YPos_mm_'  'Sep1'  'Sep2'  'x_Sep_'  'dpixel'}
           VariableTypes: ["double"    "double"    "double"    "double"    "double"    "double"]
    VariableDescriptions: {'Idx'  'YPos(mm)'  'Sep1'  'Sep2'  '<Sep>'  'dpixel'}
           VariableUnits: {}
      VariableContinuity: []
                RowNames: {}
        CustomProperties: No custom properties are set.
      Use addprop and rmprop to modify CustomProperties.

[Jason]

Thanks Chris, this is weird. Any idea why my column headings are not saving to file for me, are there any further checks I can do to help debug.

Also, I did notice when you reopend the file using readtable, the custom properties had been lost - is that correct?

[Cris LaPierre]

Yes. They are properties of the data type in MATLAB and are last when you save it as a text file.

I tested outside app designer. Try that. Can you save a table with headers when working in a script?

[Jason]

Ah thats a shame - is there any format where the properties won't be lost?

It seems writetable is more trouble than its worth - is that the only way to save data in a uitable and include the column headings? (amd be read back again)

[Jason]

"Can you save a table with headers when working in a script?"

Surely it should work in Appdesigner, or say in the document that it can't.

This is all my code.

            data=T.Data;     %  is my uitable
            class(data)      % Should be double
            try
                 [file,folder]=uiputfile({'*.csv','csv Files'},'Save Data',fullfile(app.startfolder,'TableData'));
            catch
                [file,folder]=uiputfile({'*.csv','csv Files'},'Save Data','C:\');
            end    
            app.startfolder=folder;
            savepath=fullfile(folder,file);
           
           %vn=data.ColumnName 
           %C = array2table(data,'VariableNames',vn)
           C=array2table(data); 
           T.ColumnName
           C.Properties.VariableNames=T.ColumnName;                    

           C.Properties 
           writetable(C,savepath,'WriteVariableNames', true);
           

C.Properties definetly says the variable names ar epresent, but there just not saving the file.

In the command window, I have this

           C =
           200×6 table
           Idx    Ypos(mm)     sep1      sep2     <sep>     rel<sep>
           ___    ________    ______    ______    ______    ________
           1     106.2      1811.8    1867.5    1839.7          0 
           2     106.4      1810.9    1867.3    1839.1      0.602 
           3     106.5      1811.2    1867.5    1839.4     0.3165 
           4     106.6      1814.3    1868.6    1841.5    -1.7845 
           5     106.7      1813.9    1868.9    1841.4     -1.728          
           

           ans = 
           TableProperties with properties:
           Description: ''
           UserData: []
           DimensionNames: {'Row'  'Variables'}
           VariableNames: {'Idx'  'Ypos(mm)'  'sep1'  'sep2'  '<sep>'  'rel<sep>'}
           VariableDescriptions: {}
           VariableUnits: {}
           VariableContinuity: []
           RowNames: {}
           CustomProperties: No custom properties are set.
           Use addprop and rmprop to modify CustomProperties.

[Cris LaPierre]

Depends what format you need them to be in. If you just need to save the variable so you can load it later, I would recommend saving to a mat file.

There are many options for saving to a file. writetable is a newer function that makes it simple to save tables - header line and mixed data type data. It is the option I would use writetable.

EDIT: writetable works in app designer. Just for simplicity, I have only tested your code in a script.

[Jason]

Thanks Chris - I was really excited about writetable!!, so my code above Definetly doesn't save the variable names to file. I guess the only difference between your test and mine is I have extracted the table directly from a uitable.

Is there anything else I can try to see why it doesn't

[Jason]

Even hard coding the names like this, it still doesn't

C = array2table(data,'VariableNames',{'V1', 'V2','V3', 'V4','V5', 'V6'})

[Cris LaPierre]

Just tested your original code in app designer. It works as expected for me.

My example also extracts the data from a uitable, though that doesn't appear to be relevant for the issue you are having.

Have you tried restarting MATLAB?

[Jason]

Interestingly, this does work:

T = uitable("Data",rand(10,6)*200);
T.ColumnName = {'Idx'  'YPos(mm)'  'Sep1'  'Sep2'  '<Sep>'  'dpixel'};
data=T.Data;
C=array2table(data);   % Create table format
C.Properties.VariableNames=T.ColumnName;
C
writetable(C,'F:\test.txt');

The only difference is I have all my code in a function where I pass in the table as an argument. Could this be the issue

   function saveUITable(app,T)   
            data=T.Data;          
            try
                 [file,folder]=uiputfile({'*.csv','csv Files'},'Save Data',fullfile(app.startfolder,'TableData'));
            catch
                [file,folder]=uiputfile({'*.csv','csv Files'},'Save Data','C:\');
            end
            savepath=fullfile(folder,file);     
            C = array2table(data);                
            C.Properties.VariableNames=T.ColumnName;  
            writetable(C,savepath);
   end         
            

and I call it via

   T=app.UITable;           
   saveUITable(app,T);

[Cris LaPierre]

Since your uitable is already an app object, rather than pass in T, try updating your code to

data = app.UITable.Data

and

C.Properties.VariableNames=app.UItable.ColumnName;

[Jason]

Problem solved!!!

I had a writecell command later in my code I forgot to comment out when I started using writetable. So it was working, just being over written with the write cell!

Thanks for all your help