Issue adding a header to a csv (generated using CsvWriter) in which each row summarises key information about a given trial

[m-lockwood]

I have written an expression transform which successfully maps each behaviour subject to the appropriate name, and when I use the following parameters:

this gives the following error message:

I can avoid this error message by setting append to 'True' and Overwrite to 'False', however now every trial creates one header row and one row with data.:

How can I ammend my workflow such that I can create a table with 1 header row and 1 row of data per trial without any errors?

[bruno-f-cruz]

Please attach your workflow. Thanks!

[m-lockwood]

Hi Bruno, I can't share my full workflow as it is closely adapted from someone else's code who is not ready to make it public. However, would this code snippet be enough to go on?
code_snippet.zip

Please let me know if I can clarify anything based on this.

[bruno-f-cruz]

I would need to be able to see how you are instantiating the CsvWriter from the upper level of the workflow. By you error description it sounds like you are restarting the writer on every trial (using SelectMany perhaps?). If this is the case, you need to make sure you have a different name each time you open the file or that you set it to override or append mode. If this is not the behavior you want, and you want to save all rows to the same file, consider moving the CsvWriter outside the SelectMany (or whatever higher order operator you are using). Hope it helps!

[m-lockwood]

Hi Bruno, thanks this solution worked!

The CsvWriter was indeed within a SelectMany (containing the core logic between a trial starting and ending). I replaced the data logging within this select many with a node sending a Boolean True to a behaviour subject TakeSampleData, then I used this to trigger a CsvWriter node in a GroupWorkflow on the top level of the workflow.