CODEWITHSUNDEEP
rdata.table
ribery77
ribery77

Reputation: 141

if else statement in data.table package

I have a dataset of 6 column and 4.5 millions rows. I would like to write a logical check if in the fifth column there are values with zeroes, to put 1 in the sixth column. Could you explain me how to construct an algorithm to do this? In the fifth column I found that I have cells with zero value. I want to perform if in the fifth column I have zero values to put 1 in sixth column and if not to put 0? I must use data.table package. I try with this name of the data[,6] = ifelse(name of the data[,5] == 0, 1, name of the data[,6]).

Upvotes: 2

Views: 4465

Answers (2)

akrun
akrun

Reputation: 886938

Usingdata.table, we can use :=, which would be more efficient (example data from @plafort's post)

library(data.table)#v1.9.4+
setDT(df)[X5==0, X6:=1]

Upvotes: 6

Pierre L
Pierre L

Reputation: 28441

Here's a base R way:

df[,6][df[,5] == 0] <- 1

In many cases, you can avoid having to write explicit if statements. The conditional is implied in the subset. Reading it out would say, "In the sixth column of the data frame, assign the value of 1 to all values adjacent to column five." Someone more familiar with assigning column values in data.table can easily apply it to your case.

Data

set.seed(5)
df <- data.frame(replicate(6, sample(0:5, 3)))
df[2,5] <- 0
df
  X1 X2 X3 X4 X5 X6
1  1  1  3  0  1  1
2  3  0  4  1  0  5
3  4  2  5  4  5  3

df[,6][df[,5] == 0] <- 1

df
  X1 X2 X3 X4 X5 X6
1  1  1  3  0  1  1
2  3  0  4  1  0  1
3  4  2  5  4  5  3

Upvotes: 1

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