Reading formatted data in R

Question

I am trying to use stdindata to read in R. I want to read data in the following format:

5       #rows matrix A
7       #cols matrix A
0 1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30 31 32 33 34
3       #rows matrix B
4       #cols matrix B
0 1 2 3
4 5 6 7
8 9 10 11
100     #param1
-7      #param2
9       #param3

An example of how I would like to read the data is best illustrated by the following c code:

#include <stdio.h>
#include <stdlib.h>

int* readMatrix(int rows, int cols) {
    int* matrix = (int*) malloc(rows*cols*sizeof(int));
    for (int i = 0; i < rows*cols; ++i) {
        scanf("%d", &matrix[i]);
    }
    return matrix;
}

int main() {
    int a_rows, a_cols; 
    int b_rows, b_cols;
    int *a, *b;
    int param1, param2, param3;

    scanf("%d %d", &a_rows, &a_cols);
    a = readMatrix(a_rows, a_cols);

    scanf("%d %d", &b_rows, &b_cols);
    b = readMatrix(b_rows, b_cols);

    scanf("%d %d %d", &param1, &param2, &param3);

    return 0;
}

My "equivalent" R code looks something like this:

a_rows <- scan(file="stdin", what=integer(0), n=1);
a_cols <- scan(file="stdin", what=integer(0), n=1);
A <- matrix(scan(file="stdin", n = a_rows*a_cols), a_rows, a_cols, byrow = TRUE)

b_rows <- scan(file="stdin", what=integer(0), n=1);
b_cols <- scan(file="stdin", what=integer(0), n=1);
B <- matrix(scan(file="stdin", n = b_rows*b_cols), b_rows, b_cols, byrow = TRUE)

param1 <- scan(file="stdin", what=integer(0), n=1);
param2 <- scan(file="stdin", what=integer(0), n=1);
param3 <- scan(file="stdin", what=integer(0), n=1);

Of course, this does not work, and I get the following output when I run the R script:

Read 1 item
Read 0 items
Read 0 items
Error in matrix(scan(file = "stdin", n = a_rows * a_cols), a_rows, a_cols,  :
  invalid 'ncol' value (too large or NA)
Execution halted

In fact, if I try to read only the first two values:

a_rows <- scan(file="stdin", what=integer(0), n=1);
a_cols <- scan(file="stdin", what=integer(0), n=1);

I get the following output:

Read 1 item
Read 0 items

Does anyone have a good solution to this problem? I am trying to find additional information about a function scanbut cannot find anything about why I get this behavior.

EDIT 1 I am running R version 3.1.0

R version 3.1.0 (2014-04-10) -- "Spring Dance"
Copyright (C) 2014 The R Foundation for Statistical Computing
Platform: x86_64-unknown-linux-gnu (64-bit)

EDIT 2 I found a solution, the R code is as follows:

sin <- file("stdin");
open(sin);

a_rows <- scan(sin, what=integer(0), n=1);
a_cols <- scan(sin, what=integer(0), n=1);
A <- matrix(scan(sin, n = a_rows*a_cols), a_rows, a_cols, byrow = TRUE)

b_rows <- scan(sin, what=integer(0), n=1);
b_cols <- scan(sin, what=integer(0), n=1);
B <- matrix(scan(sin, n = b_rows*b_cols), b_rows, b_cols, byrow = TRUE)

param1 <- scan(sin, what=integer(0), n=1);
param2 <- scan(sin, what=integer(0), n=1);
param3 <- scan(sin, what=integer(0), n=1);

stdin, .

Answer 1

, :

• nlines=... n=...
• file=stdin() file="stdin"
• what=integer() what=integer(0)

. , nlines=.... , , .

:

a_rows <- scan(file=stdin(), what=integer(), nlines=1);
a_cols <- scan(file=stdin(), what=integer(), nlines=1);
A <- matrix(scan(file=stdin(), nlines = a_rows), a_rows, a_cols, byrow = TRUE)
print(A)

:

> source('~/.active-rstudio-document')
1: 2
Read 1 item
1: 3
Read 1 item
1: 1
2: 2
Read 2 items
> source('~/.active-rstudio-document')
1: 2
Read 1 item
1: 3
Read 1 item
1: 1 2 3
4: 4 5 6
Read 6 items
     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6