Writetable for different data to same file

Hello,

I have a script that reads in a csv file and outputs a number of variables. I then store this variable in a table with two headings, the name of the file and in this case Time to Completion.

varNames = {'File','Time to Completion)'};
T = table(Name,TTC,'VariableNames',varNames);
writetable(T,'Time_Completion.xls');    

My problem is that I want to use this same file (Time_Completion.xls) for different runs of the script with new data so that the columns populate with every new run rather than overwriting. I don't know to read the file every time it opens and if there's data in one row go down and fill the next. Appreciate any help. Thanks.

Answer 1

[Cris LaPierre]

See the Append Data to Bottom of Table example on the writetable documentation page.

[CH]

Hi Cris, thanks for the response. I had tried append before and all I get is an error message about wrong number of arguments. I'm not very clear on how it works if I'm not manually adding a row to the table

[Cris LaPierre]

Share the code you use to create the table as well as the code you use to append the data to your existing xls file.

[CH]

[filepath,name,ext] = fileparts(fileName);
Name = convertCharsToStrings(name);

varNames = {'File','Time to Completion)'};
T = table(Name,TTC,'VariableNames',varNames);
writetable(T,'Time_Completion.xls');

I don't have any specific append code available. I was only modifying what is here.

[Cris LaPierre]

When do you get the error message? Please share the complete error message (all the red text).

From the example I linked to above, code to append to an existing files should look something like this.

writetable(newInsect,'InsectCollection.txt','WriteMode','Append',...
    'WriteVariableNames',false,'WriteRowNames',true)  

The following describes how Append behaves with spreadsheets:

• 'append' — The writing function appends the input data to the bottom of the occupied range of the specified sheet.
• If you do not specify a sheet, then the writing function appends the input data to the bottom of the occupied range of the first sheet.

[CH]

So if I change my line of code to include that line the error I get is below. Matlab version is 2021a

writetable(T,'Time_Completion.xls','WriteMode','Append');

Error using table (line 264)

Invalid parameter name: WriteMode.

[Cris LaPierre]

Do you get an error when you run the following?

InsectSpecies = {'Monarch Butterfly';'Seven-spot Ladybird';'Orchid Mantis';...
    'American Bumblebee';'Blue Dasher Dragonfly'};
InsectOrder = {'Lepidoptera';'Coleoptera';'Mantodea';'Hymenoptera';'Odonata'};
InsectFamily = {'Nymphalidae';'Coccinellidae';'Hymenopodidae';...
    'Apidae';'Libellulidae'};
PredatoryInsect = logical([0;1;1;0;1]); 

T = table(InsectSpecies,InsectOrder,InsectFamily,PredatoryInsect)

writetable(T,'InsectCollection.xls','WriteRowNames',true) 

%% Now append a new row to the table
newInsect = table({'Red-banded leafhopper'},{'Hemiptera'},{'Cicadellidae'},logical([0]));
writetable(newInsect,'InsectCollection.xls','WriteMode','Append',...
    'WriteVariableNames',false,'WriteRowNames',true)