Subscript out of bounds - general definition and solution?

matrix, r, sna

Solution

This is because you try to access an array out of its boundary.

I will show you how you can debug such errors.

- I set `options(error=recover)`

I run `reach_full_in <- reachability(krack_full, 'in')` I get :

reach_full_in <- reachability(krack_full, 'in')
Error in reach_mat[i, alter] = 1 : subscript out of bounds
Enter a frame number, or 0 to exit   
1: reachability(krack_full, "in")

I enter 1 and I get

 Called from: top level

I type `ls()` to see my current variables

  1] "*tmp*"           "alter"           "g"               
     "i"               "j"                     "m"              
    "reach_mat"       "this_node_reach"

Now, I will see the dimensions of my variables :

Browse[1]> i
[1] 1
Browse[1]> j
[1] 21
Browse[1]> alter
[1] 22
Browse[1]> dim(reach_mat)
[1] 21 21

You see that alter is out of bounds. 22 > 21 . in the line :

  reach_mat[i, alter] = 1

To avoid such error, personally I do this :

- Try to use `applyxx` function. They are safer than `for`

- I use `seq_along` and not `1:n` (1:0)

- Try to think in a vectorized solution if you can to avoid `mat[i,j]` index access.

EDIT vectorize the solution

For example, here I see that you don't use the fact that `set.vertex.attribute` is vectorized.

You can replace:

# Set vertex attributes
for (i in V(krack_full)) {
    for (j in names(attributes)) {
        krack_full <- set.vertex.attribute(krack_full, j, index=i, attributes[i+1,j])
    }
}

by this:

##  set.vertex.attribute is vectorized!
##  no need to loop over vertex!
for (attr in names(attributes))
      krack_full <<- set.vertex.attribute(krack_full, 
                                             attr, value = attributes[,attr])

Problem

When working with R I frequently get the error message "subscript out of bounds". For example: ``` # Load necessary libraries and data library(igraph) library(NetData) data(kracknets, package = "NetData") # Reduce dataset to nonzero edges krack_full_nonzero_edges <- subset(krack_full_data_frame, (advice_tie > 0 | friendship_tie > 0 | reports_to_tie > 0)) # convert to graph data farme krack_full <- graph.data.frame(krack_full_nonzero_edges) # Set vertex attributes for (i in V(krack_full)) { for (j in names(attributes)) { krack_full <- set.vertex.attribute(krack_full, j, index=i, attributes[i+1,j]) } } # Calculate reachability for each vertix reachability <- function(g, m) { reach_mat = matrix(nrow = vcount(g), ncol = vcount(g)) for (i in 1:vcount(g)) { reach_mat[i,] = 0 this_node_reach <- subcomponent(g, (i - 1), mode = m) for (j in 1:(length(this_node_reach))) { alter = this_node_reach[j] + 1 reach_mat[i, alter] = 1 } } return(reach_mat) } reach_full_in <- reachability(krack_full, 'in') reach_full_in ``` This generates the following error `Error in reach_mat[i, alter] = 1 : subscript out of bounds`. However, my question is not about this particular piece of code (even though it would be helpful to solve that too), but my question is more general: - What is the definition of a subscript-out-of-bounds error? What causes it? - Are there any generic ways of approaching this kind of error?

Original source