Based on the responses I received in Pandas SettingWithCopyWarning: I'm thoroughly confused and the clear explanation I found at Pandas - Get first row value of a given column, I thought I had all my SettingWithCopyWarning errors solved. Unfortunately, they are back (Python 3.8.5), and I'd appreciate your assistance. My dataframe df has a column 'SBPi_min_time' which I refer to as t_min
t_min
'SBPi_min_time'
df.head()
SBPi_max_time SBPi_max SBPi_min_time SBPi_min delta_p
0 52.257 119.626 55.903 111.256 8.370
1 59.513 118.580 60.562 114.395 4.185
2 62.632 119.626 63.650 112.999 6.627
3 65.721 121.021 67.279 114.395 6.626
4 69.344 120.672 72.414 113.348 7.324
If I now try to copy a value from one line of df to the previous line, I get the infamous SettingWithCopyWarning. I have tried 5 distinct approaches, and get the error in every single case. It's worth noting that the first approach is the one that is recommended in the posts that I have posted links to:
df.iloc[i, df.columns.get_loc('SBPi_min_time')] = df.iloc[i+1, df.columns.get_loc('SBPi_min_time')]
df.iloc[i, df.columns.get_loc(t_min)] = df.iloc[i+1, df.columns.get_loc(t_min)]
df.iloc[i, 3] = df.iloc[i+1, 3]
df[t_min].iloc[i] = df[t_min].iloc[i+1]
df[t_min][i] = df[t_min][i+1]
If there was a way to create a new object (in this case a float) from df[t_min][i+1], I could do so, and then set df[t_min][i] to it, but there doesn't seem to a way in which to do it:
df_copy = df.copy(deep = True)
df[t_min][i] = df_copy[t_min][i+1]
gives me the same error. What on earth am I doing wrong, and what's the fix?
Many thanks in advance
Thomas Philips
