Write a data.frame to a text file with certain format in R

Question

I am using R to access some old FORTRAN input files and have some problems about sinking a data frame into a text file and keep its format.

My approach are:

Use read.table to import data.
Adjust numbers in one column (multiply by a scalar).
Save everything back using write.table function.

My code:

con <- file(paste(pth,'/Input/met/G_test.MET', sep=""))
aaa <- read.table(con)
aaa[,2]=aaa[,2]*0.1
write.table(aaa)
close(con)

My approach failed to work because it changed the format of the input file (It ignored spaces between columns). My question: is there a good way to conduct these three steps and maintain the same format? I can use readLines to keep the format, then I have to modify all the numbers in a big loop.

Here is how the data look (I knew the number of spaces between columns):

 010192      0.00      0.04       8.3
 010292      0.33      0.02       7.5
 010392      0.61      0.23      11.7
 010492      0.00      0.04      10.0
 010592      0.00      0.07      10.6
 010692      0.00      0.02       8.9
 010792      0.00      0.19       9.4
 010892      0.00      0.30       9.4
 010992      0.00      0.08      11.4

Thanks for any suggestions.

UPDATE

Since I have to maintain the format and update numbers from one columns. I came up a 'hybrid' approach. This method worked but I appreciate suggestions on the standard approach.

Use readLines to load data as characters in order to keep the format and maintain the staring zeros.
Use read.table to load data as a data.frame and modify them

Replace numbers in a loop.

con_rain<- file(paste(pth,'/Out_Test/GA1LEVAP.MET', sep=""))
a_rain=readLines(con_rain)
b_rain=read.table(con_rain) 

for (i in 1:731){
  a_rain[i]=paste(substr(a_rain[i],1,13),sprintf("%3.2f", b_rain[i,2]*p[19]),substr(a_rain[i],18,37),sep="")
}


writeLines(a_rain, paste(pth,'/Out_Test/GA1LEVAP.MET', sep=""))

I'm confused. Did you expect write.table to behave differently than it's documented defaults? — joran
– joran, Commented Nov 19, 2012 at 23:08
@joran: Sorry for the confusion. I am trying to find the option of controlling the output format for the 'write.table' function. — TTT
– TTT, Commented Nov 20, 2012 at 2:32

Dirk is no longer here · Accepted Answer · 2012-11-19 23:15:32Z

2

Just provide a sep= argument that suits. Here is an example for 6 spaces followed by a tab:

R> head(trees)
  Girth Height Volume
1   8.3     70   10.3
2   8.6     65   10.3
3   8.8     63   10.2
4  10.5     72   16.4
5  10.7     81   18.8
6  10.8     83   19.7
R> write.table(trees, sep="      \t", 
+              file="/tmp/trees6spaces.txt", row.names=FALSE, col.names=FALSE)
R> system("head /tmp/trees6spaces.txt")
8.3         70          10.3
8.6         65          10.3
8.8         63          10.2
10.5        72          16.4
10.7        81          18.8
10.8        83          19.7
11          66          15.6
11          75          18.2
11.1        80          22.6
11.2        75          19.9
R>

answered Nov 19, 2012 at 23:15

Dirk is no longer here

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TTT Over a year ago

Thanks for the help. One more question, the space between columns are not even (The first two are six, the last one is five). So is there a way to define the format of one row and apply it to the rest of table?

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