Creating A Dataframe From A Text Dataset - regex

Question

I have a dataset that has hundreds of thousands of fields. The following is a simplified dataset
dataSet <- c("Plnt SLoc Material Description L.T MRP Stat Auto MatSG PC PN Freq Qty CFreq CQty Cur.RPt New.RPt CurRepl NewRepl Updt Cost ServStock Unit OpenMatResb DFStorLocLevel",
"0231 0002 GB.C152260-00001 ASSY PISTON & SEAL/O-RING 44 PD X A A A 18 136 30 29 50 43 24.88 51.000 EA",
"0231 0002 WH.112734 MOTOR REDUCER, THREE-PHAS 41 PD X B B A 16 17 3 3 5 4 483.87 1.000 EA X",
"0231 0002 WH.920569 SPINDLE MOTOR MINI O 22 PD X A A A 69 85 15 9 25 13 680.91 21.000 EA",
"0231 0002 GB.C150583-00001 VALVE-AIR MDI 64 PD X A A A 16 113 50 35 80 52 19.96 116.000 EA",
"0231 0002 FG.124-0140 BEARING 32 PD X A A A 36 205 35 32 50 48 21.16 55.000 EA",
"0231 0002 WP.254997 BEARING,BALL .9843 X 2.04 52 PD X A A A 18 155 50 39 100 58 2.69 181.000 EA"
)
I would like to create a dataframe out of this dataSet for further calculation. The approach I am following is as follows:
I split the dataSet by space and then recombine it.
dataSetSplit <- strsplit(dataSet, "\\s+")
The header (which is the first line) splits correctly and produces 25 characters. This can be seen by the str() function.
str(dataSetSplit)
I will then intend to combine all the rows together using the folloing script
combinedData <- data.frame(do.call(rbind, dataSetSplit))
Please note that the above script "combinedData " errors because the split did not produce equal number of fields.
For this approach to work all the fields must split correctly into 25 fields.
If you think this is a sound approach please let me know how to split the fileds into 25 fields.
It is worth mentioning that I do not like the approach of splitting the data set with the function strsplit(). It is an extremely time consuming step if used with a large data set. Can you please recommend an alternate approach to create a data frame out of the supplied data?

Answer 1

By the looks of it, you have a header row that is actually helpful. You can easily use gregexpr to calculate your "widths" to use with read.fwf.
Here's how:
## Use gregexpr to find the position of consecutive runs of spaces
## This will tell you the starting position of each column
Widths <- gregexpr("\\s+", dataSet[1])[[1]]
## `read.fwf` doesn't need the starting position, but the width of
## each column. We can use `diff` to calculate this.
Widths <- c(Widths[1], diff(Widths))
## Since there are no spaces after the last column, we need to calculate
## a reasonable width for that column too. We can do this with `nchar`
## to find the widest row in the data. From this, subtract the `sum`
## of all the previous values.
Widths <- c(Widths, max(nchar(dataSet)) - sum(Widths))
Let's also extract the column names. We could do this in read.fwf, but it would require us to substitute the spaces in the first line with a "sep" character.
Names <- scan(what = "", text = dataSet[1])
Now, read in everything except the first line. You would use the actual file instead of textConnection, I would suppose.
read.fwf(textConnection(dataSet), widths=Widths, strip.white = TRUE,
skip = 1, col.names = Names)
# Plnt SLoc Material Description L.T MRP Stat Auto MatSG PC PN Freq Qty
# 1 231 2 GB.C152260-00001 ASSY PISTON & SEAL/O-RING 44 PD NA X A A A 18 136
# 2 231 2 WH.112734 MOTOR REDUCER, THREE-PHAS 41 PD NA X B B A 16 17
# 3 231 2 WH.920569 SPINDLE MOTOR MINI O 22 PD NA X A A A 69 85
# 4 231 2 GB.C150583-00001 VALVE-AIR MDI 64 PD NA X A A A 16 113
# 5 231 2 FG.124-0140 BEARING 32 PD NA X A A A 36 205
# 6 231 2 WP.254997 BEARING,BALL .9843 X 2.04 52 PD NA X A A A 18 155
# CFreq CQty Cur.RPt New.RPt CurRepl NewRepl Updt Cost ServStock Unit OpenMatResb
# 1 NA NA 30 29 50 43 NA 24.88 51 EA <NA>
# 2 NA NA 3 3 5 4 NA 483.87 1 EA X
# 3 NA NA 15 9 25 13 NA 680.91 21 EA <NA>
# 4 NA NA 50 35 80 52 NA 19.96 116 EA <NA>
# 5 NA NA 35 32 50 48 NA 21.16 55 EA <NA>
# 6 NA NA 50 39 100 58 NA 2.69 181 EA <NA>
# DFStorLocLevel
# 1 NA
# 2 NA
# 3 NA
# 4 NA
# 5 NA
# 6 NA

Answer 2

Many thanks to Ananda Mahto, he provided many pieces to this answer.
widthMinusFirst <- diff(gregexpr('(\\s[A-Z])+', dataSet[1])[[1]])
widthFirst <- gregexpr('\\s+', dataSet[1])[[1]][1]
Width <- c(widthFirst, widthMinusFirst)
Widths <- c(Width, max(nchar(dataSet)) - sum(Width))
columnNames <- scan(what = "", text = dataSet[1])
read.fwf(textConnection(dataSet[-1]), widths = Widths, strip.white = FALSE,
skip = 0, col.names = columnNames)