Hi all, I’m trying a trivial task. Read CSV and for each row - if a value in given column is not missing, process the column. Something like this: batches = CSV.File( file; header = true, delim = ',') foreach( b ->if ! ismissing(b.Spli…

The problem here is that the iterator returned by CSV.File is immutable. So each row object that you are iterating over in your foreach loop can’t be altered. In particular, you can’t set the value Splits equal to something. Could you give more information on what your goals are? Do you want to put…

@pdeffebach , thanks for sample how to read CSV from string. Pretty useful. What I’d like to do is to read the CSV into memory and process later (merging with other CSVs, filtering rows based on the column values etc.). And then later to write the result as CSV to disk.

I think you should use DataFrames, then. Read all your files into DataFrame and then at the end write that data frame to a disk using CSV.write. batches = CSV.File( io; header = true, delim = ',') |> DataFrame

Ok, I’ll have a look into Getting Started · DataFrames.jl This will take some time :slight_smile:

You’re looking for the copycols kwarg to CSV.File although I agree that in general you’ll have an easier time doing manipulation on a DataFrame. But even if you create a DataFrame using e.g. CSV.read, you still need the copycols kwarg if you want to mutate the values later.

Just going through getting started for DataFrames and I’m a little bit confused about versions and that document. I installed (from Download Julia ) 1.4.1. The version of DataFrames is 0.20.2 (@v1.4) pkg> status Status `C:\Users\u\.julia\environments\v1.4\Project.toml` [a93c6f00] DataFrames v0.2…

I think you need to use update rather than adding the new version. Can you just try Pkg.update() and see if that bumps you to the new version? I was able to reproduce your environment on macOS and update worked for me. I would avoid adding a package using PkgSpec like that and just rely on the reso…

@pdeffebach you are right. update really worked. Thanks a lot. Now if you know why default Julia installation has stale packages, please let me know :slight_smile:

Sorry, could you clarify? Are you on JuliaPro? The new version of DataFrames was just released 2 days ago. so maybe you had installed it before then?

Read CSV and change rows later

New to Julia

pdeffebach May 6, 2020, 2:13pm 6

Please do not hesitate to ask questions!

Converting DataValues.DataValue{String} to String

Topic		Replies	Views
Update a value in DataFrames.jl New to Julia question , dataframes	2	1572	July 20, 2020
How do you edit a DataFrame after reading it from a CSV? Data	6	1118	March 1, 2021
Delete!() row from DataFrame incompatible with CSV.jl? Data dataframes , csv	3	3939	May 20, 2020
Read file with CSV.read New to Julia	8	19867	September 9, 2019
Copycols in DataFrame and CSV package not working in julia 1.7.2 New to Julia dataframes	11	519	June 1, 2022

Read CSV and change rows later

Related topics