R read.table fill empty data with value above - r

Question

I have a text file with horrible formatting that I need to read into R. I am reading a bunch of other files that don't have horrible formatting with read.table, so I would like to continue to use this function, if possible.
The file looks like this:
M D YY CONC
7 1 78 15
0.00
0.15
1.06
1.21
10.91
34.55
69.09
87.27
73.67
38.65
12.27
2.27
6.52
0.45
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.19
0.96
4.59
4.55
4.59
7.25
7.13
11.60
1.06
0.15
1.50
1.16
0.00
0.00
0.00
0.00
0.00
7 1 78 16
0.00
0.00
0.00
0.00
7.25
1.50
9.00
20.25
51.25
55.00
53.75
3.13
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.80
0.98
4.00
2.47
5.63
3.50
7.88
0.43
2.30
0.00
0.00
0.00
0.00
0.00
0.00
0.00
7 1 78 17
4.15
0.00
0.00
0.15
2.27
16.36
54.37
67.96
58.07
3.58
0.89
0.20
0.52
0.59
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
5.44
0.00
3.09
3.26
7.17
9.39
8.65
3.09
0.45
7.41
3.18
0.00
2.05
0.00
There is one CONC per hour on the date provided in the first row. My ultimate goal will be to have the date repeat and add a column for hour. So the first bit should look like:
M D YY H CONC
7 1 78 1 15
7 1 78 2 0.00
7 1 78 3 0.15
7 1 78 4 1.06
7 1 78 5 1.21
7 1 78 6 10.91
7 1 78 7 34.55
7 1 78 8 69.09
I can read in the file using this:
monitor_datai <- read.table(file =file,header = TRUE, stringsAsFactors = FALSE, skip = 0, sep = "", fill = TRUE)
BUT the issue with that approach is that the data reads in filling the first column with the month (if provided on that line) or concentration (if no month was provided for that line). Looking something like this:
head(monitor_datai)
V1 V2 V3 V4
1 7.00 1 78 15
2 0.00 NA NA NA
3 0.15 NA NA NA
4 1.06 NA NA NA
5 1.21 NA NA NA
6 10.91 NA NA NA
So, I need help reading in the file and fixing the formatting.
Thanks!

Answer 1

Here is my approach, using the weapons of the data.table-package
I was not sure what the values of H shuld become... just 1:128, of a sequency by group, or ...? Please specify and I'll add it into the answer..
I included comments and in between results in the code below, so you (hopefully) can follow the steps and adjust if/where needed
library( data.table )
#read the file as-is, complete lines, no separator
DT <- fread( "./temp/testfile.txt", sep = "", skip = 1, header = FALSE )
# head(DT)
# V1
# 1: 7 1 78 15
# 2: 0.00
# 3: 0.15
# 4: 1.06
# 5: 1.21
# 6: 10.91
#get column names from the file, store in a vector
colnames = names( fread( "./temp/testfile.txt", sep = " ", nrows = 1, header = TRUE ) )
#split the rows with a space in them to the for desired columns,
# use a space (or multiple in a row) as separator
DT[ grepl(" ", V1), (colnames) := tstrsplit( V1, "[ ]+", perl = TRUE ) ]
# V1 M D YY CONC
# 1: 7 1 78 15 7 1 78 15
# 2: 0.00 <NA> <NA> <NA> <NA>
# 3: 0.15 <NA> <NA> <NA> <NA>
# 4: 1.06 <NA> <NA> <NA> <NA>
# 5: 1.21 <NA> <NA> <NA> <NA>
# ---
# 124: 7.41 <NA> <NA> <NA> <NA>
# 125: 3.18 <NA> <NA> <NA> <NA>
# 126: 0.00 <NA> <NA> <NA> <NA>
# 127: 2.05 <NA> <NA> <NA> <NA>
# 128: 0.00 <NA> <NA> <NA> <NA>
#where CONC is.na, copy the value of V1
DT[ is.na( CONC ), CONC := V1 ]
# V1 M D YY CONC
# 1: 7 1 78 15 7 1 78 15
# 2: 0.00 <NA> <NA> <NA> 0.00
# 3: 0.15 <NA> <NA> <NA> 0.15
# 4: 1.06 <NA> <NA> <NA> 1.06
# 5: 1.21 <NA> <NA> <NA> 1.21
# ---
# 124: 7.41 <NA> <NA> <NA> 7.41
# 125: 3.18 <NA> <NA> <NA> 3.18
# 126: 0.00 <NA> <NA> <NA> 0.00
# 127: 2.05 <NA> <NA> <NA> 2.05
# 128: 0.00 <NA> <NA> <NA> 0.00
#now we can drop the V1-column
DT[, V1 := NULL]
#set all columns to the right (numeric) type
DT[, (names(DT)) := lapply( .SD, as.numeric ) ]
#and fill down the missing values of M, D and YY
setnafill( DT, type = "locf", cols = c("M", "D", "YY") )
# M D YY CONC
# 1: 7 1 78 15.00
# 2: 7 1 78 0.00
# 3: 7 1 78 0.15
# 4: 7 1 78 1.06
# 5: 7 1 78 1.21
# ---
# 124: 7 1 78 7.41
# 125: 7 1 78 3.18
# 126: 7 1 78 0.00
# 127: 7 1 78 2.05
# 128: 7 1 78 0.00