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This is what I have:

id<-c(1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2)

measure<-c("speed","weight","time","speed","weight","time","speed","weight","time",

           "speed","weight","time","speed","weight","time","speed","weight","time")

value<-c(1.23,10.3,33,1.44,10.4,31,1.21,10.1,33,4.25,12.5,38,1.74,10.8,31,3.21,10.3,33)

testdf<-data.frame(id,measure,value) 

This is what I want:

id<-c(1,1,1,2,2,2)  

speed<-c(1.23,1.44,1.21,4.25,1.74,3.21)

weight<-c(10.3,10.4,10.1,12.5,10.8,10.3)

time<-c(33,31,33,37,31,33)

res<-data.frame(id,speed,weight,time) 

The issue lies in that my variables speed weight and time are repeated. I can get it done with a for loop with if statements but its a major headache and not very efficient. This is my first post on stackoverflow ... long time user first time question ... thanks yall!

1 Answer

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by (38.5k points)

Here, use rowid from data.table 

library(reshape2)

 

testdf$r <- data.table::rowid(testdf$measure); 

dcast(testdf, id + r ~ measure)

 

  id r speed time weight

1  1 1  1.23   33   10.3

2  1 2  1.44   31   10.4

3  1 3  1.21   33   10.1

4  2 4  4.25   38   12.5

5  2 5  1.74   31   10.8

6  2 6  3.21   33   10.3

1.In one line 

dcast(testdf, id + data.table::rowid(measure) ~ measure).

 

2.Without data.table

 testdf$r <- ave(testdf$id, testdf$meas, FUN = seq_along).

3. For learning the data.table package, refer to the below code:

library(data.table)

setDT(testdf)

testdf[, r := rowid(measure)]

dcast(testdf, id + r ~ measure)

If you wish to learn more about how to use python for data science, then go through this data science python course by Intellipaat for more insights.

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