set gxout stat
d set fwrite out.dat ; set gxout fwrite;
d rh). Or the output goes to the script variable
result which
can be parsed inside a script (see the corr.gs GrADS
script)The output allows many statistical calculations to be made. Here's an example of opening up a global model file and looking at the 1000 mb relative humidity, statistically,
ga-> set gxout stat
ga-> d rh
Data Type = grid
Dimensions = 0 1
I Dimension = 1 to 145
J Dimension = 1 to 73
Sizes = 145 73 10585
Undef value = 1e+20
Undef count = 0 Valid count = 10585
Min, Max = 0.0610352 100.061
Stats(sum,sumsqr,n): 787381 6.35439e+07 10585
Stats(sum,sumsqr)/n: 74.3865 6003.2
Stats(sum,sumsqr)/(n-1): 74.3935 6003.77
Stats(sigma,var)(n): 21.6761 469.854
Stats(sigma,var)(n-1): 21.6771 469.898
Cmin, cmax, cint = 10 100 10Let's break it down:
Data Type = grid ----- you have a grid
Dimensions = 0 1 ----- the dimension type for the variable
0 - lon 1 - lat 2 - lev 3 - time 1 - not varying
I Dimension = 1 to 145 ------ obvious
J Dimension = 1 to 73
Sizes = 145 73 10585 ------- 10585 is 145*73
or total number of points
Undef value = 1e+20 ------- undefined value
Undef count = 0 Valid count = 10585 ----- # of defined and
undefined points in the grid. Remember that if GrADS can't find
any data it returns undefs. This is useful for checking if you
have any data, Valid count = 0 means no...
Min, Max = 0.0610352 100.061 ---- UHHH OHHHH! we have slight
supersaturation..
Stats(sum,sumsqr,n): 787381 6.35439e+07 10585 - This
should
be fairly obvious, sum = the simple sum of all defined points.
sumsqr = sum of, in this case, rh*rh and
10585 is n.
Stats(sum,sumsqr)/n: 74.3865 6003.2 - Divide by
n for convenience, the first number is the "biased"
mean...
Stats(sum,sumsqr)/(n-1): 74.3935 6003.77 - the so called
unbiased mean (remove 1 degree of freedom), etc.
Stats(sigma,var)(n): 21.6761 469.854 - the standard
deviation
and variance "biased" (n)
Stats(sigma,var)(n-1): 21.6771 469.898 - the standard
deviation and variance "unbiased" (n-1)
Cmin, cmax, cint = 10 100 10 - What GrADS will use when
contouring.
gridded and
station data