# Calculating monthly averages from daily precipitation data

I have a raster brick for daily precipitation data and I need to convert it to monthly data, how would I go about doing this? Each layer is a day and there are 34698 days (i.e. too many to go through manually and create monthly averages by listing mean(raster1, raster 2... etc)

``````class      : RasterBrick

dimensions : 64, 58, 3712, 34698  (nrow, ncol, ncell, nlayers)

resolution : 0.44, 0.44  (x, y)

extent     : 12.1, 37.62, -45.54, -17.38  (xmin, xmax, ymin, ymax)

crs        : NA

source     : C:/Users/teyah/AppData/Local/Temp/RtmpQBzpnO/raster/r_tmp_2020-08-13_121709_23408_66253.grd

names      : Precipitation.1, Precipitation.2, Precipitation.3, Precipitation.4, Precipitation.5, Precipitation.6, Precipitation.7, Precipitation.8, Precipitation.9, Precipitation.10, Precipitation.11, Precipitation.12, Precipitation.13, Precipitation.14, Precipitation.15, ...

min values :    0.000000e+00,    0.000000e+00,    0.000000e+00,    0.000000e+00,    0.000000e+00,    0.000000e+00,    0.000000e+00,    0.000000e+00,    0.000000e+00,     0.000000e+00,     0.000000e+00,     0.000000e+00,     0.000000e+00,     0.000000e+00,     0.000000e+00, ...

max values :    6.533941e-04,    1.833772e-04,    8.561218e-04,    1.070062e-03,    7.177751e-04,    6.058318e-04,    5.470571e-04,    1.588907e-03,    1.674356e-03,     1.091221e-03,     5.895557e-04,     3.984022e-04,     4.418955e-04,     3.041818e-04,     2.085147e-04, ...
``````
• Take a look at the `rts` package. There are specific functions for aggregating raster timeseries data to different summary periods. Aug 18, 2020 at 14:08

Use `zApply` with `by=as.yearmon`. `as.yearmon` is available in the `zoo` package.