GRASS GIS manual: r.series

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NAME

r.series - Makes each output cell value a function of the values assigned to the corresponding cells in the input raster map layers.

KEYWORDS

raster, series

SYNOPSIS

r.series
r.series help
r.series [-qn] input=name[,name,...] output=name[,name,...] method=string[,string,...] [quantile=float[,float,...]] [threshold=float[,float,...]] [range=lo,hi] [--overwrite] [--verbose] [--quiet]

Flags:

-q: Run quietly
-n: Propagate NULLs
--overwrite: Allow output files to overwrite existing files
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

input=name[,name,...]: Name of input raster map(s)
output=name[,name,...]: Name for output raster map
method=string[,string,...]: Aggregate operation; Options: average,count,median,mode,minimum,min_raster,maximum,max_raster,stddev,range,sum,threshold,variance,diversity,slope,offset,detcoeff,quart1,quart3,perc90,quantile,skewness,kurtosis
quantile=float[,float,...]: Quantile to calculate for method=quantile; Options: 0.0-1.0
threshold=float[,float,...]: Threshold to calculate for method=threshold
range=lo,hi: Ignore values outside this range

DESCRIPTION

r.series makes each output cell value a function of the values assigned to the corresponding cells in the input raster map layers. Following methods are available:

average: average value

count: count of non-NULL cells

median: median value

mode: most frequently occuring value

minimum: lowest value

maximum: highest value

range: range of values (max - min)

stddev: standard deviation

sum: sum of values

variance: statistical variance

diversity: number of different values

slope: linear regression slope

offset: linear regression offset

detcoeff: linear regression coefficient of determination

min_raster: raster map number with the minimum time-series value

max_raster: raster map number with the maximum time-series value

NOTES

With -n flag, any cell for which any of the corresponding input cells are NULL is automatically set to NULL (NULL propagation). The aggregate function is not called, so all methods behave this way with respect to the -n flag.

Without -n flag, the complete list of inputs for each cell (including NULLs) is passed to the aggregate function. Individual aggregates can handle data as they choose. Mostly, they just compute the aggregate over the non-NULL values, producing a NULL result only if all inputs are NULL.

The min_raster and max_raster methods generate a map with the number of the raster map that holds the minimum/maximum value of the time-series. The numbering starts at 0 up to n for the first and the last raster listed in input=, respectively.

If the range= option is given, any values which fall outside that range will be treated as if they were NULL. The range parameter can be set to low,high thresholds: values outside of this range are treated as NULL (i.e., they will be ignored by most aggregates, or will cause the result to be NULL if -n is given). The low,high thresholds are floating point, so use -inf or inf for a single threshold (e.g., range=0,inf to ignore negative values, or range=-inf,-200.4 to ignore values above -200.4).

Linear regression (slope, offset, coefficient of determination) assumes equal time intervals. If the data have irregular time intervals, NULL raster maps can be inserted into time series to make time intervals equal (see example).

Number of raster maps to be processed is given by the limit of the operating system. For example, both the hard and soft limits are typically 1024. The soft limit can be changed with e.g. ulimit -n 1500 (UNIX-based operating systems) but not higher than the hard limit. If it is too low, you can as superuser add an entry in

/etc/security/limits.conf
# <domain>      <type>  <item>         <value>
your_username  hard    nofile          1500

This would raise the hard limit to 1500 file. Be warned that more files open need more RAM.

EXAMPLES

Using r.series with wildcards:

r.series input="`g.mlist pattern='insitu_data.*' sep=,`" \
         output=insitu_data.stddev method=stddev

Note the g.mlist script also supports regular expressions for selecting map names.

Using r.series with NULL raster maps:

r.mapcalc "dummy = null()"
r.series in=map2001,map2002,dummy,dummy,map2005,map2006,dummy,map2008 \
         out=res_slope,res_offset,res_coeff meth=slope,offset,detcoeff

Example for multiple aggregates to be computed in one run (3 resulting aggregates from two input maps):

r.series in=one,two out=result_avg,res_slope,result_count meth=sum,slope,count

Example for counting the number of days above a certain temperature using daily average maps ('???' as DOY wildcard):

r.series input=`g.mlist rast pat="temp_2003_???_avg" sep=,` \
         output=temp_2003_days_over_25deg range=25.0,100.0 method=count

AUTHOR

Glynn Clements

Last changed: $Date: 2012-03-02 05:54:55 -0800 (Fri, 02 Mar 2012) $

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