CODEWITHSUNDEEP
julia
penguinyaay1
penguinyaay1

Reputation: 45

Julia beginner: Iterate getindex() for increasing indices

I'm working with a 121x137 (i,j) array (mortality table) and am trying to create a 121x1 vector from this made up of the (i+1,j+1) values (i.e. index (50,50), (51,51) and so forth.

I'm using the following code - BaseTable is my 121x137 array:

age=50    
survivalcurve = for i in age:nrow(BaseTable)-1
    for j in age:ncol(BaseTable)-1
        println(getindex(FemaleBaseTable, i+1, j+1))
    end
    end

However, when I do this, its returning all values of i and j - if I picture the values I want as a diagonal line running top-bottom, L-R of my table, its giving me all the values on the top right of my imaginary diagonal line.

If I fix i and loop through j, it works and returns the entire 50th row:

age=50
survivalcurve =
    for j in age:ncol(FemaleBaseTable)
        println(getindex(FemaleBaseTable, 50, j+1))
    end

and likewise if I fix j and loop through i, this works and returns the entire jth column:

age=50

survivalcurve =
    for i in age:nrow(FemaleBaseTable)-1
        println(getindex(FemaleBaseTable, i+1, 50))
    end

I've surmised its returning all values because I'm using age:nrow / age:ncol, but not sure what a suitable replacement would be to only return the (i+1),(j+1) value would be. Any help would be appreciated!

Upvotes: 0

Views: 131

Answers (1)

AboAmmar
AboAmmar

Reputation: 5559

You can collect the diagonal elements starting at any index (i,j) by using either diag from LinearAlgebra.jl or manually using a single loop.

Assuming you have:

nrows, ncols = 121, 137
FemaleBaseTable = rand(nrows, ncols)

# And the diagonal should start at any (i,j)
i, j = 50, 50

You can either use

diag(@view FemaleBaseTable[i:end,j:end])

or,

[FemaleBaseTable[i,i] for (i,j) in zip(i:nrows,j:ncols)]

Upvotes: 2

Related Questions