Computing value just for the last row of same value of column

Question

I use the following code:

    i1 <- SRC2[, Co:= as.character(round(sum(Exist)/.N, 2)) , 
               sequenceID][, .I[1:(.N-1)], sequenceID]$v1


    SRC2[i1, Co:= '']
    SRC2

I would to change the line code so only the last occurrence of the same values of sequenceID will contain the Co value and not all the lines as in this code.

The current output (each line has value "Co"): "

sequenceID" "transactionID" "eventID" "items"  "Exist" "Co"
"1" 42207993       1577          1        "OV50"     1     0.67
"2" 42207993       6048          2        "OV11"     0     0.67
"3" 42207993       1597          3        "OV148"    1     0.67
"4" 57237976       12423         1        "OV46"     0     0.5
"5" 57237976       12589         2        "OV197"    1     0.5

The required output (only the last line of the same "sequenceID" contains value "Co":

"sequenceID" "transactionID" "eventID" "items"  "Exist" "Co"
"1" 42207993       1577          1        "OV50"     1
"2" 42207993       6048          2        "OV11"     0  
"3" 42207993       1597          3        "OV148"    1       0.67
"4" 57237976       12423         1        "OV46"     0
"5" 57237976       12589         2        "OV197"    1       0.5

Avi · Accepted Answer · 2015-11-23 12:29:51Z

1

Here is the required code:

library(data.table)
setDT(SRC2)

i1 <- SRC2[, Co:= as.character(round(sum(Exist)/.N, 2)) , sequenceID][, .I[1:(.N-1)], sequenceID]$V1

SRC2[i1, Co:= '']
SRC2

The last part of i1 has to contain V1 (in Capital letter)

edited Nov 23, 2015 at 12:29

answered Nov 23, 2015 at 11:51

Avi

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