Created
March 17, 2019 01:56
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script to edit and save statistics from raster maps in GRASS GIS, using r.stats
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# import modules | |
import grass.script as grass | |
def export_statistics(input_map = ''): | |
''' | |
Function to calculate and export statistics (using r.stats) from landscape metrics maps. | |
Results are given in hectares. | |
Parameters | |
---------- | |
input_map: string | |
Landscape metric map from which statistics will be calculated. | |
Returns | |
------- | |
out: txt file | |
File with the id of the patch (or class), the area (or correspondent metric), in hectares, | |
and the percentage of the total each patch correponds. | |
''' | |
# Define region | |
grass.run_command('g.region', rast=input_map) | |
# Calculate area and percentage statistics for the input map using r.stats | |
x = grass.read_command('r.stats', flags = 'nap', input = input_map) | |
# Separating values by line | |
y = x.split('\n') | |
# Initialize arrays | |
idd = [] | |
areas = [] | |
if len(y) != 0: | |
# For each element in the list of values | |
for i in y: | |
if i != '': | |
##print i | |
# Split by space | |
f = i.split(' ') | |
##print f | |
# Get id (raster value) | |
ids = f[0] | |
ids = int(ids) | |
idd.append(ids) | |
##print ids | |
# Get area in m2 and transform to hectares | |
ha = f[1] | |
haint = float(ha) | |
haint = haint/10000 | |
areas.append(haint) | |
##print haint | |
# Calculate the percentage | |
percentages = [float(i)/sum(areas) for i in areas] | |
# Open output file | |
txt_file = open(input_map+'.txt', 'w') | |
# Write header | |
txt_file.write('CODE'+','+'AREA_HA'+','+'PROPORTION\n') | |
# For each element | |
for i in range(len(idd)): | |
# Write line in the output file | |
txt_file.write(`idd[i]`+','+`areas[i]`+','+`percentages[i]`+'\n') | |
# Close the output file | |
txt_file.close() | |
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