Hi, I need to calculate the percent difference between two rasters. Below is my code and I am getting the following error. Can somebody help me to correct my code? Thanks in advance. Error: Traceback ( most recent call last ) : File "C:\Users\jayaskeradl\Desktop\Arkansas Flood\My_Phyton_Scripts\Normal_Difference.py" , line 73 , in module > outcalc2 = Minus ( normal , fmaskrasters ) File "c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\sa\Functions.py" , line 4247 , in Minus in_raster_or_constant2 ) File "c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\sa\Utils.py" , line 53 , in swapper result = wrapper ( * args , ** kwargs ) File "c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\sa\Functions.py" , line 4244 , in Wrapper [ "Minus" , in_raster_or_constant1 , in_raster_or_constant2 ] ) TypeError : expected a raster or layer name months = [ 10 ] weeks = [ 1 ] year = [ 2010 ] arcpy . env . workspace = r 'H:\PRISM_800m_weekly_sum\Crawford\All' out = r 'H:\PRISM_800m_weekly_sum\Crawford\All\output' for month in months : for week in weeks : arcpy . env . workspace = r 'H:\PRISM_800m_weekly_sum\Crawford\All' fmaskrasters = arcpy . ListRasters ( "Week_" + str ( week ) + "_Sum" + str ( year ) + "_" + str ( month ) + "*" , "*" ) arcpy . env . workspace = r 'H:\PRISM_800m_weekly_sum\Crawford\All\output' normal = arcpy . ListRasters ( "Crawford_Normal_Week_" + str ( week ) + "_*_" + str ( month ) + "*" ) outcalc2 = Minus ( normal , fmaskrasters ) Final = ( outcalc2 / normal ) * 100 finras1 = out + "\\" + "Crawford_Normal_Week_" + str ( week ) + "_Difference" + "_" + str ( month ) + ".tif" arcpy . CopyRaster_management ( Final , finras1 + "_Normal_Difference_Crawford.tif" , "" , "" , "" , "" , "" )

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Problem in Calculate percent difference between two rasters

DuminduJayasekera

Hi,

I need to calculate the percent difference between two rasters. Below is my code and I am getting the following error. Can somebody help me to correct my code?

Thanks in advance.

Error:

Traceback <SPAN class="punctuation token">(</SPAN>most recent call last<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp; File <SPAN class="string token">"C:\Users\jayaskeradl\Desktop\Arkansas Flood\My_Phyton_Scripts\Normal_Difference.py"</SPAN><SPAN class="punctuation token">,</SPAN> line <SPAN class="number token">73</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">in</SPAN> <SPAN class="operator token"><</SPAN>module<SPAN class="operator token">></SPAN>
&nbsp;&nbsp;&nbsp; outcalc2 <SPAN class="operator token">=</SPAN> Minus<SPAN class="punctuation token">(</SPAN>normal<SPAN class="punctuation token">,</SPAN> fmaskrasters<SPAN class="punctuation token">)</SPAN>
&nbsp; File <SPAN class="string token">"c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\sa\Functions.py"</SPAN><SPAN class="punctuation token">,</SPAN> line <SPAN class="number token">4247</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">in</SPAN> Minus
&nbsp;&nbsp;&nbsp; in_raster_or_constant2<SPAN class="punctuation token">)</SPAN>
&nbsp; File <SPAN class="string token">"c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\sa\Utils.py"</SPAN><SPAN class="punctuation token">,</SPAN> line <SPAN class="number token">53</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">in</SPAN> swapper
&nbsp;&nbsp;&nbsp; result <SPAN class="operator token">=</SPAN> wrapper<SPAN class="punctuation token">(</SPAN><SPAN class="operator token">*</SPAN>args<SPAN class="punctuation token">,</SPAN> <SPAN class="operator token">**</SPAN>kwargs<SPAN class="punctuation token">)</SPAN>
&nbsp; File <SPAN class="string token">"c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\sa\Functions.py"</SPAN><SPAN class="punctuation token">,</SPAN> line <SPAN class="number token">4244</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">in</SPAN> Wrapper
&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">[</SPAN><SPAN class="string token">"Minus"</SPAN><SPAN class="punctuation token">,</SPAN> in_raster_or_constant1<SPAN class="punctuation token">,</SPAN> in_raster_or_constant2<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>
TypeError<SPAN class="punctuation token">:</SPAN> expected a raster <SPAN class="operator token">or</SPAN> layer name‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

months <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="number token">10</SPAN><SPAN class="punctuation token">]</SPAN>
weeks <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN>
year <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="number token">2010</SPAN><SPAN class="punctuation token">]</SPAN>

arcpy<SPAN class="punctuation token">.</SPAN>env<SPAN class="punctuation token">.</SPAN>workspace <SPAN class="operator token">=</SPAN> r<SPAN class="string token">'H:\PRISM_800m_weekly_sum\Crawford\All'</SPAN> 
out <SPAN class="operator token">=</SPAN> r<SPAN class="string token">'H:\PRISM_800m_weekly_sum\Crawford\All\output'</SPAN>

<SPAN class="keyword token">for</SPAN> month <SPAN class="keyword token">in</SPAN> months<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">for</SPAN> week <SPAN class="keyword token">in</SPAN> weeks<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp; arcpy<SPAN class="punctuation token">.</SPAN>env<SPAN class="punctuation token">.</SPAN>workspace <SPAN class="operator token">=</SPAN> r<SPAN class="string token">'H:\PRISM_800m_weekly_sum\Crawford\All'</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp; fmaskrasters <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>ListRasters<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"Week_"</SPAN> <SPAN class="operator token">+</SPAN> str<SPAN class="punctuation token">(</SPAN>week<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">"_Sum"</SPAN> <SPAN class="operator token">+</SPAN> str<SPAN class="punctuation token">(</SPAN>year<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">"_"</SPAN> <SPAN class="operator token">+</SPAN> str<SPAN class="punctuation token">(</SPAN>month<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">"*"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">"*"</SPAN><SPAN class="punctuation token">)</SPAN>

&nbsp;&nbsp;&nbsp; arcpy<SPAN class="punctuation token">.</SPAN>env<SPAN class="punctuation token">.</SPAN>workspace <SPAN class="operator token">=</SPAN> r<SPAN class="string token">'H:\PRISM_800m_weekly_sum\Crawford\All\output'</SPAN> 
&nbsp;&nbsp;&nbsp; normal <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>ListRasters<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"Crawford_Normal_Week_"</SPAN> <SPAN class="operator token">+</SPAN> str<SPAN class="punctuation token">(</SPAN>week<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">"_*_"</SPAN> <SPAN class="operator token">+</SPAN> str<SPAN class="punctuation token">(</SPAN>month<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">"*"</SPAN><SPAN class="punctuation token">)</SPAN>
&nbsp;&nbsp;&nbsp; outcalc2 <SPAN class="operator token">=</SPAN> Minus<SPAN class="punctuation token">(</SPAN>normal<SPAN class="punctuation token">,</SPAN> fmaskrasters<SPAN class="punctuation token">)</SPAN>
&nbsp;&nbsp;&nbsp; Final <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">(</SPAN>outcalc2<SPAN class="operator token">/</SPAN>normal<SPAN class="punctuation token">)</SPAN><SPAN class="operator token">*</SPAN><SPAN class="number token">100</SPAN>
&nbsp;&nbsp;&nbsp; finras1 <SPAN class="operator token">=</SPAN> out <SPAN class="operator token">+</SPAN> <SPAN class="string token">"\\"</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">"Crawford_Normal_Week_"</SPAN> <SPAN class="operator token">+</SPAN> str<SPAN class="punctuation token">(</SPAN>week<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">"_Difference"</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">"_"</SPAN> <SPAN class="operator token">+</SPAN> str<SPAN class="punctuation token">(</SPAN>month<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="string token">".tif"</SPAN>
&nbsp;&nbsp;&nbsp; arcpy<SPAN class="punctuation token">.</SPAN>CopyRaster_management<SPAN class="punctuation token">(</SPAN>Final<SPAN class="punctuation token">,</SPAN>finras1 <SPAN class="operator token">+</SPAN> <SPAN class="string token">"_Normal_Difference_Crawford.tif"</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">""</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">""</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">""</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">""</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">""</SPAN><SPAN class="punctuation token">)</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

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DuminduJayasekera

I am selecting one raster layer using the week, month and year defined in the main script. Therefore, "normal" and "fmaskrasters" have one raster layer. I have revised the code with what you said but still I am getting the same error.

DarrenWiens2

Well, you can only use Minus to find the difference between two rasters, not two lists of rasters, so you can either put the Minus inside a loop or somehow summarize the lists into a summary raster beforehand.

DuminduJayasekera

Thanks for the reply. My rasters are located in two different work spaces. I want to obtain the percent differences for the corresponding week rasters. For example, long term weekly avarege rasters are read as normals and the weekly rasters for each year are located in fmaskrasters. I am getting the two rasters correct in the above code but when I run Minus(normal,fmaskrasters) it gives the error mentioned above.

Normal Rasters<SPAN class="punctuation token">:</SPAN>
Crawford_Normal_Week_1_1981_2016_10<SPAN class="punctuation token">.</SPAN>tif
Crawford_Normal_Week_2_1981_2016_10<SPAN class="punctuation token">.</SPAN>tif
Crawford_Normal_Week_3_1981_2016_10<SPAN class="punctuation token">.</SPAN>tif
Crawford_Normal_Week_4_1981_2016_10<SPAN class="punctuation token">.</SPAN>tif
Crawford_Normal_Week_5_1981_2016_10<SPAN class="punctuation token">.</SPAN>tif

Weekly Rasters<SPAN class="punctuation token">:</SPAN>
Week_1_Sum1981_10_Crawford<SPAN class="punctuation token">.</SPAN>tif
<SPAN class="punctuation token">.</SPAN>
<SPAN class="punctuation token">.</SPAN>
Week_5_Sum1981_10_Crawford<SPAN class="punctuation token">.</SPAN>tif
<SPAN class="punctuation token">.</SPAN>
<SPAN class="punctuation token">.</SPAN>

Week_1_Sum2010_10_Crawford<SPAN class="punctuation token">.</SPAN>tif
Week_2_Sum2010_10_Crawford<SPAN class="punctuation token">.</SPAN>tif
Week_3_Sum2010_10_Crawford<SPAN class="punctuation token">.</SPAN>tif
Week_4_Sum2010_10_Crawford<SPAN class="punctuation token">.</SPAN>tif
Week_5_Sum2010_10_Crawford<SPAN class="punctuation token">.</SPAN>tif
<SPAN class="punctuation token">.</SPAN>
<SPAN class="punctuation token">.</SPAN>
Week_1_Sum2016_10_Crawford<SPAN class="punctuation token">.</SPAN>tif
<SPAN class="punctuation token">.</SPAN>
<SPAN class="punctuation token">.</SPAN>
Week_5_Sum2016_10_Crawford<SPAN class="punctuation token">.</SPAN>tif

Percent Difference <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">(</SPAN>Week_1_Sum2010_10_Crawford<SPAN class="punctuation token">.</SPAN>tif <SPAN class="operator token">-</SPAN> Crawford_Normal_Week_1_1981_2016_10<SPAN class="punctuation token">.</SPAN>tif<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">/</SPAN> Crawford_Normal_Week_1_1981_2016_10<SPAN class="punctuation token">.</SPAN>tif<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">*</SPAN><SPAN class="number token">100</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

DarrenWiens2

arcpy.ListRasters() returns a list of rasters, but Minus wants two individual rasters. If you just want the first (and, presumably, only?) raster, use arcpy.ListRasters()[0].

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