The M3DIFF program performs comparison (and other) operations on pairs of variables from a user-specified pair of GRIDDED I/O API files and computes statistics for each specified variable and for the specified “difference” operation. An I/O API output file containing all the results of the specified operations can be optionally generated for viewing within scientific visualization tools.
setenv <infile A> <path name>
setenv <infile B> <path name>
setenv <reportfile> <path name>
m3diff [<infile A> <infile B> [<reportfile>]] [<DEFAULT>]
The default statistical analysis is a tabular listing (by time period) of the maximum value, minimum value, mean value, and the standard deviation of the 2 datasets. Several other calculations are also available:
| Pointwise difference: | a-b |
| Pointwise difference: | b-a |
| Pointwise ratio: | a/b |
| Pointwise ratio: | b/a |
| Pointwise absolute value of difference: | |a-b| |
| Difference normalized by 1st grid: | (a-b)/a |
| Difference normalized by 2nd grid: | (a-b)/b |
| Difference normalized by 2nd grid: | (b-a)/b |
| Absolute value of difference normalized by A: | |a-b|/a |
| Absolute value of difference normalized by B: | |a-b|/b |
| Difference normalized by pointwise mean: | (a-b)/0.5(a+b) |
| Difference normalized by pointwise mean: | (b-a)/0.5(a+b) |
| Difference normalized by joint root mean square: | (a-b)/RMS(a&b) |
| Difference normalized by joint root mean square: | (b-a)/RMS(a&b) |
| Pointwise sum | a+b |
| Pointwise maximum | max(a,b) |
| Pointwise minimum | min(a,b) |