CODEWITHSUNDEEP
rfor-loopdata.table
Gin_Salmon
Gin_Salmon

Reputation: 847

Creating columns with a for loop

I've got a column in a data table which I'd like to repeat for 17 years. I want to get this same set of values into a column and name it.

More precisely, my data is as follows, it is called "mean_exp_TOD".

     TheInterval mean_Exports 
 1:           0 0.000000e+00   
 2:           1 0.000000e+00   
 3:           2 0.000000e+00   
 4:           3 0.000000e+00   
 5:           4 0.000000e+00   
 6:           5 0.000000e+00   
 7:           6 0.000000e+00   
 8:           7 0.000000e+00   
 9:           8 3.278689e-05   
10:           9 6.933060e-03   
11:          10 1.747746e-01   
12:          11 1.330710e+00   
13:          12 4.628286e+00   
14:          13 1.097312e+01   
15:          14 2.067735e+01   
16:          15 3.214487e+01   
17:          16 4.381565e+01   
18:          17 5.434046e+01   
19:          18 6.208044e+01   
20:          19 6.807106e+01   
21:          20 7.212614e+01   
22:          21 7.434484e+01   
23:          22 7.452706e+01   
24:          23 7.376302e+01   
25:          24 7.110812e+01   
26:          25 6.784952e+01   
27:          26 6.270421e+01   
28:          27 5.503787e+01   
29:          28 4.597257e+01   
30:          29 3.537733e+01   
31:          30 2.398188e+01   
32:          31 1.262636e+01   
33:          32 4.892807e+00   
34:          33 1.284960e+00

What I want is to create a new data table with one column called "TheInterval", which takes the values from my snippet. Then I just want to create a columns based on Years.

What i've been doing is:

Years <- c(1999:2016)


 for (i in Years){
     mean_EXP <- mean_exp_TOD[, list(Interval = c(0:47), i = mean_exp_TOD[,mean_Exports])]
 }

This however returns : (I cut it short just for explanatory reasons)

  Interval            i
 1:        0 0.000000e+00
 2:        1 0.000000e+00
 3:        2 0.000000e+00
 4:        3 0.000000e+00
 5:        4 0.000000e+00
 6:        5 0.000000e+00
 7:        6 0.000000e+00
 8:        7 0.000000e+00
 9:        8 3.278689e-05

No errors or warnings either.

So instead of getting 17 columns named "1999", "2000", "2001".... filled with the mean_Exports data, I only get one called i!

Any help?

Upvotes: 0

Views: 67

Answers (2)

akrun
akrun

Reputation: 887991

We can just do (if we don't need to use a for loop)

mean_exp_TOD[, paste0(Years) := mean_Exports]
tail(mean_exp_TOD)
#   TheInterval mean_Exports      1999      2000      2001      2002      2003      2004      2005      2006      2007      2008      2009      2010      2011
#1:          28    45.972570 45.972570 45.972570 45.972570 45.972570 45.972570 45.972570 45.972570 45.972570 45.972570 45.972570 45.972570 45.972570 45.972570
#2:          29    35.377330 35.377330 35.377330 35.377330 35.377330 35.377330 35.377330 35.377330 35.377330 35.377330 35.377330 35.377330 35.377330 35.377330
#3:          30    23.981880 23.981880 23.981880 23.981880 23.981880 23.981880 23.981880 23.981880 23.981880 23.981880 23.981880 23.981880 23.981880 23.981880
#4:          31    12.626360 12.626360 12.626360 12.626360 12.626360 12.626360 12.626360 12.626360 12.626360 12.626360 12.626360 12.626360 12.626360 12.626360
#5:          32     4.892807  4.892807  4.892807  4.892807  4.892807  4.892807  4.892807  4.892807  4.892807  4.892807  4.892807  4.892807  4.892807  4.892807
#6:          33     1.284960  1.284960  1.284960  1.284960  1.284960  1.284960  1.284960  1.284960  1.284960  1.284960  1.284960  1.284960  1.284960  1.284960
#        2012      2013      2014      2015      2016
#1: 45.972570 45.972570 45.972570 45.972570 45.972570
#2: 35.377330 35.377330 35.377330 35.377330 35.377330
#3: 23.981880 23.981880 23.981880 23.981880 23.981880
#4: 12.626360 12.626360 12.626360 12.626360 12.626360
#5:  4.892807  4.892807  4.892807  4.892807  4.892807
#6:  1.284960  1.284960  1.284960  1.284960  1.284960

Upvotes: 3

Shape
Shape

Reputation: 2952

mean_EXP <- data.table(Interval = 1:47)
for(i in Years) {
    mean_EXP[,as.character(i) := mean_exp_TOD[,mean_Exports]]
}

EDIT: I assume you're doing this so you can do a more complicated selection, with each year dependent on the previous year? otherwise, you can create them all at once with something like:

mean_EXP[,as.character(Years) := replicate(length(Years),
                                          mean_exp_TOD[,mean_Exports],
                                          simplify = FALSE)]

Upvotes: 2

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