Hello, 

I'm using the champ.load to read and filter my data and it works well. However when I want to proceed with the champ.QC I receive an error because the column "Sample_Group" in the csv file provided is empty. 

So I tried to add the information of that column ("first" or "second") and use the modified csv file to load the idat files. However at that point I'm getting the following error:

"Error in champ.import(directory, arraytype = arraytype) : Error Match between pd file and Green Channel IDAT file."

I went through the pipeline to check how ChAMP imports the data but I did not manage to pick which is the mistake. I know It would be great if you could help so that I can include this information and proceed with champ.QC. 

Thank you,

Olga Giannakopoulou 

Hello Olga:

Firstly, champ.QC() failed because of lacing of Sample_Group column, which could because your csv file does not contain Sample_Group. That's OK because different research have different column name on most interested covariates. In champ.QC() there should be a parameter called "pheno", you just need to change it as myLoad$pd$your_phenotype, then it should be good. 

Another question about loading is:

Based on my experience, the most possible error is because you used Excel to open original CSV file, then added information on that, then same it as CSV again. By doing this, original Sentrix_ID (a very long number) could be changed. I guess it's some format problem with Excel.

Than after you modify the file, ChAMP will load your csv file, then get Sentrix_ID and Sentrix_Position, and map them to IDAT data, since Sentrix_ID has changed, no IDAT file would be matched.

I think this is the most possible reason. Please check you modified CSV file and original one, focus on the Sentrix_ID column.

If not this reason, I would check closer into code.

Best

Yuan Tian

Before editing the excel sheet (adding sample group data) press ctrl+1, then under "category" see that "NUMBER" is pressed. then press F2 and "ENTER". now enter your'e sample group data, save and "champ.load()". this way you can make sure that "sentrix_ID" stays "NUMERIC". Roi Horwitz