How to use function to create new dataframe column using other column values?

Question

I have a list of DOIs and Journal titles in a csv, now in a dataframe. I'm trying to reconstruct the journal url for v1 of the articles using a function. What is the correct way to create a new column using a function that uses values from existing columns in the dataframe?

The dataframe looks like this:

PMID    Journal     DOI
1234    medRxiv     10.1101/2020.09.30.320762
2345    bioRxiv     10.1101/2020.05.26.117549

The function I created:

def createURL (doi, journal) :
    url = 'https://www.'+journal+'.org/content/'+ str(doi)+'v1'
    
    return url

My attempt to call the function:

#this returns a Key Error ('PMID')
for row in dfRxiv :
    dfRxiv['URL'][row] = createURL(dfRxiv['DOI'][row], dfRxiv['Journal'][row])

I'm new to Python and I'm sure there's a better way to do this - I appreciate any help!

jamesh · Accepted Answer · 2020-11-27 18:28:51Z

1

You're pretty much there. You don't need to iterate through the rows or define a function - it's easier than that!:

dfRxiv['URL'] = 'https://www.' + dfRxiv['Journal'].astype('str') + '.org/content/' + dfRxiv['DOI'].astype('str') + 'v1'

edit If you do want to use a function:

def createURL(df):
    url = 'https://www.' + df['Journal'].astype('str') + '.org/content/' + df['DOI'].astype('str') + 'v1'
    return url

dfRxiv['URL'] = createURL(dfRxiv)

edited Nov 27, 2020 at 18:28

answered Nov 27, 2020 at 18:21

jamesh

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