topic Re: R script to read query/table in Developer

R script to read query/table

neldarov — Mon, 19 Aug 2019 11:21:17 GMT

I am trying to read one of the query output/table using R inside script box:

x <- table1$"Col1"

I get this error message: Details: "ADO.NET: R script error. Error: object 'Table1' not found Execution halted

Can someone tell me how to read it?

Re: R script to read query/table

dm-p — Mon, 19 Aug 2019 21:38:38 GMT

Hi @neldarov,

Are you using the R script visual? If so, the data is exposed a dataframe named dataset. Please refer to step #3 in this linked article for reference.

As long as your field name is Col1 then the following would work:

x <- dataset$"Col1"

I've tested with a recent dataset, and the editor will show any fields as part of autocomplete, e.g.: for my test dataset:

Note this code doesn't fully work in Power BI Desktop as it doesn't produce a plot (yet) but it does work if I debug in RStudio, e.g.:

Hopefully this should be all you need.

Good luck!

Daniel

Re: R script to read query/table

neldarov — Tue, 20 Aug 2019 04:03:09 GMT

Thanks, but I am using just an R script not visuals. I need to save the table as an csv file using R script.

Re: R script to read query/table

dm-p — Tue, 20 Aug 2019 05:19:46 GMT

Hi - can you please advise where in Power BI Desktop you're running the script? Presumably Power Query if not within visuals?
Thanks,
Daniel

Re: R script to read query/table

neldarov — Tue, 20 Aug 2019 05:21:57 GMT

Yes, within query.

It works within visuals. However I would like to do some data analysis in R and then save it.

Re: R script to read query/table

dm-p — Tue, 20 Aug 2019 05:52:27 GMT

Righto - you'd do something like this (assuming the destination directory exists):

If the destination directory doesn't exist, you'll get a script error. Once you click okay, you'll get a .csv file in the specified directory, e.g.:

Here's an article that explains in more detail.

Regards,

Daniel

Re: R script to read query/table

neldarov — Tue, 20 Aug 2019 06:00:20 GMT

The article does not tell what the "dataset" is))

The whole point of my question is this "dataset":

the error here is: Error in is.data.frame(x) : object 'dataset' not found

I need to take a table or another query or another data within Power Bi

Re: R script to read query/table

dm-p — Tue, 20 Aug 2019 06:03:21 GMT

Can you please perhaps post an example of your query/R code? I tested the above with a query I had open in Power BI Desktop and it worked as documented.

The R Script transformation exposes the current step's data as an dataframe called dataset, which should be all you need, unless there is a specific transformation in your query that alters this?

Thanks,

Daniel

Re: R script to read query/table

neldarov — Tue, 20 Aug 2019 06:09:42 GMT

There is no code to share:

I have one SQL query (which is saved as a table) and I need to save it using R script.

So simple, isn't it?

What is dataset, who creates it? I have no idea.

Re: R script to read query/table

dm-p — Tue, 20 Aug 2019 07:29:36 GMT

It is simple 🙂

The dataset dataframe is made available to the R Transform by Power Query.

I'll see if I can break down further by walking through - here's my query after I connect to a table in my database (supplying SQL in the connection dialog will produce something similar if it runs successfully):

SQL Results

I create a folder called test in the root directory of my hard disk, e.g.:

Empty 'test' folder

In Power Query, I select Transform from the ribbon and then Run R script, e.g.:

Invoking the 'Run R script' transform

I'm now prompted to provide my code. The pre-filled comment in the text box tells me that dataset holds the input data (results of the previous step, i.e. my table), e.g.:

Empty dialog weith pre-filled comment

I want to save the output from my SQL query as results.csv in the test subfolder I created earlier, so I add the code to do this. Because Power Query tells me I can use dataset for this, I can add this to my R code, e.g.:

Utilising the 'dataset' dataframe that Power Query has informed me about

When I click OK, my code will run. Here's what my query looks like now:

I can then navigate to my folder to check I have a file:

results.csv present in my folder

I can verify this is correct by opening it, e.g.:exported .csv in VS Code

Now I know this works, I can refresh my data in Power BI Desktop any time I like and the file will be overwritten in the target location, e.g.:File after refreshing my data, with updated timestamp

I'm hoping that this clarifies things end-to-end.

Regards,

Daniel

Re: R script to read query/table

neldarov — Tue, 20 Aug 2019 08:43:33 GMT

thanks a lot!