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RE: absolute minimum value selection

LarissaPizzolato

Hello,

I have a file geodatabase table with a field titled "min_value". Within this field there are values from -1000 to +1000. I am trying to search all of the rows in the table to select the row with the lowest absolute value within the "min_value" field (ie. value +/- closest to zero). I will then be using a value (shapefile name) within the same row (but different field) to identify which shapefile to use in the next processing step of the script.

Any help is greatly appreciated!

Thank-you!

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Accepted answers

MathewCoyle

There may be a better way, but here's the best solution I could find.

curs =  arcpy.SearchCursor(table) for row in curs:     listing.append(row.min_value)  print min((abs(0 - i), i) for i in listing)[1]

You could also pass the OID or some other identifier to go back to the row object.

All comments

MathewCoyle

Ah yes, makes sense. Doesn't really matter if they are positive or negative if they are the same absolute value anyways.

curtvprice

Looks good, much more fleshed out. Maybe I am missing something though, this doesn't seem to preserve the negative sign with the xmin assignment.

You're right--it doesn't preserve the sign.

I don't think you need it as long as you use the ABS function in the second SearchCursor SQL expression.

Arc 10 help: SQL reference for query expressions used in ArcGIS

MathewCoyle

Matt - I guess I have a tweak:

tv = arcpy.MakeTableView(table)
curs =  arcpy.SearchCursor(tv)
listing = list() # create a list
for row in curs:
    listing.append(row.min_value)
del row, curs # always a good idea when done!
xmin = min([abs(i) for i in listing])
# now get that record (or the first if several) with that abs value
curs = SearchCursor(tv,"abs(%s) = %s" % (min_value,xmin))
# get the value for field "shapefile"
shapefile = curs.next().shapefile
del curs

Looks good, much more fleshed out. Maybe I am missing something though, this doesn't seem to preserve the negative sign with the xmin assignment.

curtvprice

Matt - I guess I have a tweak:

tv = arcpy.MakeTableView(table)
curs =  arcpy.SearchCursor(tv)
listing = list() # create a list
for row in curs:
    listing.append(row.min_value)
del row, curs # always a good idea when done!
xmin = min([abs(i) for i in listing])
# now get that record (or the first if several) with that abs value
curs = SearchCursor(tv,"abs(%s) = %s" % (min_value,xmin))
# get the value for field "shapefile"
shapefile = curs.next().shapefile
del curs

MathewCoyle

There may be a better way, but here's the best solution I could find.

curs =  arcpy.SearchCursor(table) for row in curs:     listing.append(row.min_value)  print min((abs(0 - i), i) for i in listing)[1]

You could also pass the OID or some other identifier to go back to the row object.

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