Calculates and removes the mean of the (rightmost) dimension at all other dimensions.
function dim_rmvmean ( x : numeric ) return_val [dimsizes(x)] : float or double
A variable of numeric type and any dimensionality.
The output is of type double if the input is double, and float otherwise.
The dimensionality is the same as the input dimensionality.
The dim_rmvmean function calculates and removes the mean from all elements of the n-1th (rightmost) dimension for each index of the dimensions 0...n-2. Missing values are ignored.
Use dim_rmvmean_n if you want to specify which dimension(s) to remove the mean from.
Use dim_rmvmean_Wrap if retention of metadata is desired.
Example 1: Let x be a 1-dimensional array: (a) Create a new variable, xNew, that contains just the deviations from the mean; (b) replace the variable x with the deviations.
xNew = dim_rmvmean(x) ; new variable x = dim_rmvmean(x) ; overwrite with deviationsExample 2: Let x be a 3-dimensional array with dimension sizes (ntim, nlat, nlon). To remove the means of the "nlon" dimension:
xRmvLon = dim_rmvmean (x) ; new variable containing deviations (no metadata) xRmvLon = dim_rmvmean_Wrap( x ) ; with metadata x = dim_rmvmean (x) ; overwrite with deviationsExample 3: Let x be a 3-dimensional array with named dimensions (time, lat, lon) and dimension sizes (ntim, nlat, nlon). To remove the mean of the time dimension from all lat/lon indices, use NCL's Named Subscripting to reorder the input array such that "time" is the rightmost dimension.
Note: in V5.1.1, you will be able to use dim_rmvmean_n to avoid having to reorder your data.
xRmvTime = dim_rmvmean(x(lat|:, lon|:, time|:)) xRmvTime = dim_rmvmean_Wrap(x(lat|:, lon|:, time|:)) xRmvTime = dim_rmvmean_n(x,0) ; no reordering needed xRmvTime = dim_rmvmean_n_Wrap(x,0)Example 4: Let x be as in Example 3 and let x contain monthly means for (say) 10 years of data (ntim=120). Monthly anomalies for each month could be calculated using array subscripting and Named Subscripting to reorder the input array such that "time" is the rightmost dimension.
xRmvJan = dim_rmvmean_Wrap(x(lat|:, lon|:, time|0:ntim-1:12)) xRmvJuly = dim_rmvmean_Wrap(x(lat|:, lon|:, time|6:ntim-1:12)) xRmvJan = dim_rmvmean_n_Wrap(x0:ntim-1:12,:,:),0) ; no reordering needed xRmvJuly = dim_rmvmean_n_Wrap(x(6:ntim-1:12,:,:),0)