Grid Indexing Convention

(Example for Ni = 20, Nj = 20)

Written by Paul Bourke
November 1997

Grid is characterised by the number of cells horizontally Ni and vertically Nj

Grids are saved to files in "cell number" order where

cell number = j * Ni + i
For example

for (j=0;j<Nj;j++)
   for (i=0;i<Ni;i++)
      printf("%g",grid[i][j]);

Calculate indices (i,j) from the cell number as follows

i = cell number % Ni
j = cell number / Ni