How to read a data file with 2 dimensional data interspersed with comments, in R

read_jho.R

#' Read JHo
#' 
#' Read in a file formatted like Jennifer's data sets
#' 
#' @param file a character indicating the file name (and possibly path)
#' @param n_nrows integer indicating number of rows for each matrix
#' @param n_matrices integer indicating number of matrices in the file
#' @param n_comment integer indicating the number of comment lines preceding each matrix of data; should include blank lines
#' @param n_top_comment integer indicating the number of comment lines that are unique to the start of the file; default is 0 lines
#' @param ... arguments to be passed to \code{scan}, such as \code{what=numeric()} and \code{sep=","}
#' 
#' @details
#' Jennifer said she had a file that had several matrices interspersed with text comments. This is an approach that I think should help read in that data set
#' 
#' Arguments to \code{scan} need to be specified. To read in example data, I used \code{read_jho(file_name, 7, 5, 3, 1, what=numeric(), sep=",")}.
#' 
#' @return
#' Returns an array whose first two dimensions are equal to the dimensions of each matrix, and the size of the third dimension is the number of matrices
#' 
#' @export
read_jho <- function(file, n_rows, n_matrices, n_comment, n_top_comment=0, ...){
	stopifnot(file.exists(file)) # check that file exists

	data_read <- list()
	for(i in 1:n_matrices){
		line_start <- (i-1)*(n_comment+n_rows) + n_comment + n_top_comment
		data_read[[i]] <- scan(file, skip=line_start, nlines=n_rows, ...)
		data_read[[i]] <- as.numeric(data_read[[i]])
		data_read[[i]] <- matrix(data_read[[i]], nrow=n_rows, byrow=TRUE)
	}

	data_array <- simplify2array(data_read)
	
	return(data_array)
}

read_jho_script.R

# =========
# = Setup =
# =========

# ---- Data Dimensions ----
# All used for generating fake file
# Only 2 needed to read in the fake file
n_columns <- 3 # don't need to know for reading in
n_rows <- 7 # needed for reading
n_matrices <- 5 # needed for reading

# ---- Prepare Content ----
# Numeric Content
# Create a shorthand function for generating random numeric matrix (nm)
# This function uses R's scoping to find the dimensions, rather than
# the dimensions being supplied as arguments to the function
make_nm <- function(){matrix(rnorm(n_rows*n_columns), nrow=n_rows, ncol=n_columns)}

# Below is version of function that requires you to supply the 2 arguments
# I.e., make_nm() doesn't work with the function below, but works with the one above
# For below, have to do make_nm(7, 3), e.g.
# make_nm <- function(mat_rows, mat_columns){matrix(rnorm(mat_rows*mat_columns), nrow=mat_rows, ncol=mat_columns)}

# Gibberish/ Header Content
# Define gibberish values to be ignored when reading
# Could be any text that needs to be skipped
# If text has really weird characters, could maybe cause problems?
# This is simple example, though
animal_matrix <- matrix(c("cat","dog","sheep"),ncol=1)


# ===============
# = Create File =
# ===============

# ---- Create File ----
# Define File Name
file_name <- "~/Desktop/jho_test.csv"

# Create file (no append)
# V1 is an arbitrary fake header text
# I don't want to append (write new file)
# I don't want row or column names (just adds extra junk)
write.table("V1", file=file_name, append=FALSE, row.names=FALSE, col.names=FALSE) # creates file, V1 only
n_top_comment <- 1 # because I'm adding just 1 "V1" line at top

# ---- Add to File ----
# Add to file (append)
for(i in 1:n_matrices){ # loop through, adding lines
	# Now append is true, because adding extra lines to file
	write.table(animal_matrix, file=file_name, append=TRUE, row.names=FALSE, col.names=FALSE) # gibberish
	write.table(make_nm(), file=file_name, append=TRUE, row.names=FALSE, col.names=FALSE, sep=",") # numeric
}


# =============
# = Read File =
# =============

# ---- Data Dimensions Needed for Read ----
# See "Setup" Section Above
n_comment <- nrow(animal_matrix) # these would be gibberish comments to skip

# ---- Read Data 1 Matrix at a Time ----
# Create empty list
data_read <- list()

# Loop and Read
for(i in 1:n_matrices){
	# Determine Line of File to Start Reading for this Iteration
	lines_read_previously <- (i-1)*(n_comment+n_rows) + n_top_comment
	line_start <- lines_read_previously + n_comment
	
	# Read in Desired Portion of File
	# The 'sep' argument should refer to what separates values in the numeric part 
	# See the `write.table(make_nm(), ...` piece of code under 'Add to File' section above
	data_read[[i]] <- scan(file_name, skip=line_start, nlines=good_lines, what=numeric(), sep=",") 
	
	# Format to Matrix
	# The value returned from `scan()` is a vector
	# The number of columns is inferred; can be set explicitly for clarity, if known
	data_read[[i]] <- matrix(data_read[[i]], nrow=good_lines, byrow=TRUE)
}


# =============================================
# = Take Element-Wise Average Across Matrices =
# =============================================

# Format to array
data_array <- simplify2array(data_read)

# Take average
data_array_mean <- apply(data_array, c(1,2), mean)

@jahoey OK I made changes that fixed the code. I was counting lines incorrectly, but was getting away with it in my toy example just do to a coincidence (that's what I get for testing more scenarios!).

I changed some of the names of things in the script file to match what I called them in the function, so they're more consistent now.

I got the code to work for both the 'Excel' and the 'amphiprion' versions of the data --- if you're using the original format of the data (what you said came from amphiprion) DO NOT specify the sep= argument (It wasn't tab delimited). If it's the .csv from the Excel Save As, then use sep=",".

Here is the line of code I used to run in the example data set in the "from amphiprion" format:

read_jho(file="~/Desktop/jho_test.txt", n_rows=3, n_matrices=3, n_comment=2, n_top_comment=13, what="character")

Note that I had to make a weird formatting change once I saw your actual data ---- the values are expressed as -2.064e-05, which doesn't read in nicely if I specify what=numeric() like I had before. What I've done inside the function is to do a as.numeric() on whatever is read in, so that allows me to specify what="character" and still output a numeric array.

The "jho_test.txt" test file should be attached to this comment; if not, I'll just paste it into the following comment.

I think this should all work now. Let me know.

EDIT: Example File
Open TextEdit and copy paste the following, and save as "jho_test.txt" to your Desktop, then my example above should run.

===== BAYENV2.0 =====

input file is set
number of populations is set
number of iterations is set
seed is set
TEST = 0 . So running matrix estimation
MCMC VER 0.71 (THREADED)
ITERATIONS = 100000
INPUT FILE = for_bayenv.txt
SEED = -4441

num_alleles = 2274.000000
number of loci = 1137
VAR-COVAR MATRIX: ITER = 500
3.658524e-03    5.511923e-05    -2.603048e-04   
5.511923e-05    3.682494e-03    -2.102286e-04   
-2.603048e-04   -2.102286e-04   3.842626e-03    

VAR-COVAR MATRIX: ITER = 1000
3.773501e-03    -3.427948e-05   -2.089264e-05   
-3.427948e-05   3.607002e-03    4.486956e-05    
-2.089264e-05   4.486956e-05    3.636913e-03

VAR-COVAR MATRIX: ITER = 1000
3.771e-03    -3.448e-05   -2.064e-05   
-3.448e-05   3.602e-03    4.486e-05    
-2.064e-05   4.486e-05    3.613e-03