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So the following piece of code will do what we want in a more general way:
| Code Block | ||
|---|---|---|
| ||
precip = read("precip.grib")
n = count(precip)
precip_3h = precip[2, n] - precip[1, n-1]
return precip_3h |
Visualise the macro. Your plot may be blank! There is one more trick: we have created a derived field, and this changes the automatic scaling algorithm used when plotting. Precipitation is stored in metres, but we want to display it in mm. Modify the precip_shade icon and set:
| Grib Scaling of Derived Fields | On |
Visualise you your macro result again and confirm that you now have precipitation only for the 3-hour periods, which does not accumulate with each frame.
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