Using loops with a 3d array in R - beginner-CodePudding

Edit: It had cut the top line of code, sorry.

I'm trying to make a very simple loop for an array. For each time period, I want it to take the amount for g in the last period and double it. The error I get is that it doesn't like the dimensions. But i've tried a number of things, nothing I've tried works.

Edit: So g in period1 should be 20, in period2 it should be 40, in period3 80, in period4 160.

g=20
d=10
t=0.1*d
c=t

#Number of periods
nPeriods = 4

#central vector
B = c(g,t,c,d)

#central array
column.names = c('aaaaaaa', 'bbbbbb')
row.names = c('ggggg', 'hhhhh')
matrix.names = c(1:nPeriods)
C = array(c(B), dim=c(2, 2, nPeriods),
          dimnames = list(row.names, column.names, matrix.names))

print(C)
#make a slice to view as data table
G = C[,,1]


for (i in 2:nPeriods){
  g[,,i]=g[,,i-1]*2
}

H = C[,,3]

CodePudding user response：

If you remove the requirement for g, with a few things updated, this code works. I don't know what output you were expecting, though. I added the output here, along with the code. If something isn't what you were expecting, let me know by updating your question and leaving a comment so that I know that you did (SO sends a message with a comment).

d=10
t=0.1*d
c=t

#Number of periods
# nPeriods = 4      <- commented out, used 3
nPeriods = 3

#central vector
# B = c(g,t,c,d)    <- commented out, used t, c, and d
B = c(t, c, d)
# [1]  1  1 10

Without g here, you get a 3 dimensional array, which from your question seems like what you wanted.

#central array
column.names = c('aaaaaaa', 'bbbbbb')
row.names = c('ggggg', 'hhhhh')
matrix.names = c(1:nPeriods)
C = array(c(B), dim=c(2, 2, nPeriods),
          dimnames = list(row.names, column.names, matrix.names))

print(C) 
# , , 1
# 
#       aaaaaaa bbbbbb
# ggggg       1     10
# hhhhh       1      1
# 
# , , 2
# 
#       aaaaaaa bbbbbb
# ggggg       1      1
# hhhhh      10      1
# 
# , , 3
# 
#       aaaaaaa bbbbbb
# ggggg      10      1
# hhhhh       1     10
#  

#make a slice to view as data table
G = C[,,1]
#       aaaaaaa bbbbbb
# ggggg       1     10
# hhhhh       1      1

Since there was no g and it would not have been the right dimensions if it were used in B, I changed this to the only object with the right dimensions: C.

for (i in 2:nPeriods){
  C[,,i]=C[,,i-1]*2    # instead of g... C
}
C
# , , 1
# 
#       aaaaaaa bbbbbb
# ggggg       1     10
# hhhhh       1      1
# 
# , , 2
# 
#       aaaaaaa bbbbbb
# ggggg       2     20
# hhhhh       2      2
# 
# , , 3
# 
#       aaaaaaa bbbbbb
# ggggg       4     40
# hhhhh       4      4
#  

H = C[,,3]
#       aaaaaaa bbbbbb
# ggggg       4     40
# hhhhh       4      4

CodePudding user response：

I think you need to change this:

for (i in 2:nPeriods){
  g[,,i]=g[,,i-1]*2
}

to this:

for (i in 2:nPeriods){
  C[,,i]=C[,,i-1]*2
}