CODEWITHSUNDEEP
r
Kiran Solanki
Kiran Solanki

Reputation: 21

R: Creating a 2x2 matrix using a dataframe for each row

I am a bit of a R noob here hahaha. I need to create a polygon defined by a 2 column array with decimalised longitude (west of 0 = negative) in column 1 and decimalised latitude in column 2. The data is found in 4 columns in my dataframe (LonT,LonB,LatR and LatL), what I want is my matrix to resemble something like this:

     [1]   [2]
[1] LonT  LatR
[2] LonB  LatL

However, I am unsure of how to get this to work. This would then have to be run for each row in my dataframe.

Here's the header for my dataframe:

  Ctry Year   SR   Lat   Lon PType PNum  Catch LonT LonB LatR LatL
1   DE 1998 29D8 50.25 -11.5     M    1 23.862  -11  -12 50.5 50.0
2   DE 1998 34D7 52.75 -12.5     M    1 42.499  -12  -13 53.0 52.5
3   DE 1998 34D8 52.75 -11.5     M    1 35.794  -11  -12 53.0 52.5
4   DE 1998 36D9 53.75 -10.5     M    1 23.862  -10  -11 54.0 53.5
5   DE 1998 43F7 57.25   7.5     M    1  0.017    8    7 57.5 57.0
6   DE 1998 45F4 58.25   4.5     M    1  0.058    5    4 58.5 58.0

Upvotes: 1

Views: 1215

Answers (1)

akrun
akrun

Reputation: 887831

We can split the subset of dataset by the sequence of rows and convert to a list of matrixes.

lst <- lapply(split(df1[9:12], seq_len(nrow(df1))), matrix, ncol=2)
lst[1:2]
#$`1`
#     [,1] [,2]
#[1,] -11  50.5
#[2,] -12  50  

#$`2`
#    [,1] [,2]
#[1,] -12  53  
#[2,] -13  52.5

data

df1 <- structure(list(Ctry = c("DE", "DE", "DE", "DE", "DE", "DE"), 
Year = c(1998L, 1998L, 1998L, 1998L, 1998L, 1998L), SR = c("29D8", 
"34D7", "34D8", "36D9", "43F7", "45F4"), Lat = c(50.25, 52.75, 
52.75, 53.75, 57.25, 58.25), Lon = c(-11.5, -12.5, -11.5, 
-10.5, 7.5, 4.5), PType = c("M", "M", "M", "M", "M", "M"), 
PNum = c(1L, 1L, 1L, 1L, 1L, 1L), Catch = c(23.862, 42.499, 
35.794, 23.862, 0.017, 0.058), LonT = c(-11L, -12L, -11L, 
-10L, 8L, 5L), LonB = c(-12L, -13L, -12L, -11L, 7L, 4L), 
LatR = c(50.5, 53, 53, 54, 57.5, 58.5), LatL = c(50, 52.5, 
52.5, 53.5, 57, 58)), .Names = c("Ctry", "Year", "SR", "Lat", 
"Lon", "PType", "PNum", "Catch", "LonT", "LonB", "LatR", "LatL"
 ), class = "data.frame", row.names = c("1", "2", "3", "4", "5", 
 "6"))

Upvotes: 1

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