Deleting rows that are duplicated in one column based on the conditions of another column

Question

Here is an example of my data set;

Date      Time(GMT)Depth Temp  Salinity Density Phosphate
24/06/2002  1000    1           33.855          0.01
24/06/2002          


        

Answer 1

Lets say you have data in df

df = df[order(df[,'Date'],-df[,'Depth']),]
df = df[!duplicated(df$Date),]