How to have all elements of text file processed in R - r

Question

I have a single text file, NPFile, that contains 100 different newspaper articles that is 3523 lines in length. I am trying to pick out and parse different data fields for each article for text processing. These fields are: Full text: Publication date:, Publication title: etc....
I am using grep to pick out the different lines that contain the data fields I want. Although I can get the line numbers (start and end positions of the fields), I am getting an error when I try to use the line numbers to extract the actual text and put it into a vector:
#Find full text of article, clean and store in a variable
findft<-grep ('Full text:', NPFile, ignore.case=TRUE)
endft<-grep ('Publication date:', NPFile)
ftfield<-(NPFile[findft:endft])
The last line ftfield<-(NPFile[findft:endft] is giving this warning message:
1: In findft:endft :
numerical expression has 100 elements: only the first used
The starting findft and ending points endft each contain 100 elements, but as the warning indicated, ftfield only contains the first element (which is 11 lines in length). I was assuming (wrongly/mistakenly) that the respective lines for each 100 instances of the full text field would be extracted and stored in ftfield - but obviously I have not coded this correctly. Any help would be appreciated.
Example of Data (These are the fields and data associated with one of the 100 in the text file):
Waiting for the 500-year flood; Red River rampage: Severe weather events, new records are more frequent than expected.
Full text: AS THE RED River raged over makeshift dikes futilely erected against its wrath in North Dakota, drowning cities beneath a column of water 26 feet above flood level, meteorologists were hard pressed to describe its magnitude in human chronology.
A 500-year flood, some call it, a catastrophic weather event that would have occurred only once since Christopher Columbus arrived on the shores of the New World. Whether it could be termed a 700-year flood or a 300-year flood is open to question.
The flood's size and power are unprecedented. While the Red River has ravaged the upper Midwest before, the height of the flood crest in Fargo and Grand Forks has been almost incomprehensible.
But climatological records are being broken more rapidly than ever. A 100-year-storm may as likely repeat within a few years as waiting another century. It is simply a way of classifying severity, not the frequency. "There isn't really a hundred-year event anymore," states climatologist Tom Karl of the National Oceanic and Atmospheric Administration.
Reliable, consistent weather records in the U.S. go back only 150 years or so. Human development has altered the Earth's surface and atmosphere, promoting greater weather changes and effects than an untouched environment would generate by itself.
What might be a 500-year event in the Chesapeake Bay is uncertain. Last year was the record for freshwater gushing into the bay. The January 1996 torrent of melted snowfall into the estuary recorded a daily average that exceeded the flow during Tropical Storm Agnes in 1972, a benchmark for 100-year meteorological events in these parts. But, according to the U.S. Geological Survey, the impact on the bay's ecosystem was not as damaging as in 1972.
Sea level in the Bay has risen nearly a foot in the past century, three times the rate of the past 5,000 years, which University of Maryland scientist Stephen Leatherman ties to global climate warming. Estuarine islands and upland shoreline are eroding at an accelerated pace.
The topography of the bay watershed is, of course, different from that of the Red River. It's not just flow rates and rainfall, but how the water is directed and where it can escape without intruding too far onto dry land. We can only hope that another 500 years really passes before the Chesapeake region is so tested.
Pub Date: 4/22/97
Publication date: Apr 22, 1997
Publication title: The Sun; Baltimore, Md.
Title: Waiting for the 500-year flood; Red River rampage: Severe weather events, new records are more frequent than expected.:   [FINAL Edition ]
From this data example above, ftfield has 11 lines when I examined it:
[1] "Full text: AS THE RED River raged over makeshift dikes futilely erected against its wrath in North Dakota, drowning cities beneath a column of water 26 feet above flood level, meteorologists were hard pressed to describe its magnitude in human chronology."
[2] "A 500-year flood, some call it, a catastrophic weather event that would have occurred only once since Christopher Columbus arrived on the shores of the New World. Whether it could be termed a 700-year flood or a 300-year flood is open to question."
[3] "The flood's size and power are unprecedented. While the Red River has ravaged the upper Midwest before, the height of the flood crest in Fargo and Grand Forks has been almost incomprehensible."
[4] "But climatological records are being broken more rapidly than ever. A 100-year-storm may as likely repeat within a few years as waiting another century. It is simply a way of classifying severity, not the frequency. \"There isn't really a hundred-year event anymore,\" states climatologist Tom Karl of the National Oceanic and Atmospheric Administration."
[5] "Reliable, consistent weather records in the U.S. go back only 150 years or so. Human development has altered the Earth's surface and atmosphere, promoting greater weather changes and effects than an untouched environment would generate by itself."
[6] "What might be a 500-year event in the Chesapeake Bay is uncertain. Last year was the record for freshwater gushing into the bay. The January 1996 torrent of melted snowfall into the estuary recorded a daily average that exceeded the flow during Tropical Storm Agnes in 1972, a benchmark for 100-year meteorological events in these parts. But, according to the U.S. Geological Survey, the impact on the bay's ecosystem was not as damaging as in 1972."
[7] "Sea level in the Bay has risen nearly a foot in the past century, three times the rate of the past 5,000 years, which University of Maryland scientist Stephen Leatherman ties to global climate warming. Estuarine islands and upland shoreline are eroding at an accelerated pace."
[8] "The topography of the bay watershed is, of course, different from that of the Red River. It's not just flow rates and rainfall, but how the water is directed and where it can escape without intruding too far onto dry land. We can only hope that another 500 years really passes before the Chesapeake region is so tested."
[9] "Pub Date: 4/22/97"
[10] ""
[11] "Publication date: Apr 22, 1997"
And, lastly, findft[1] corresponds with endft[1] and so on until findft[100] and endft[100].

Answer 1

I'll assume that findft will contain several indexes as well as endft. I'm also assuming that both of them have the same length and that they are paired by the same index ( e.g. findft[5] corresponds to endft[5]) and that you want all NPfile elements between these two indexes as well as the other pairs.
If this is so, try:
ftfield = lapply(1:length(findft), function(x){ NPFile[findft[x]:endft[x]] })
This will return a list. I can't guarantee that this will work because there is no data example to work with.

Answer 2

We can do this with Map. Get the sequence of values for each corresponding element of 'findft' to 'endft', then subset the 'NPFile' based on that index
Map(function(x, y) NPFile[x:y], findft, endft)