topic Re: Would like to create star and snowflake symbols in Python Questions

Would like to create star and snowflake symbols

SteveCline — Wed, 28 Oct 2015 23:10:50 GMT

I am trying to replicate a technique used in the attached photo which uses what they call, "star and snowflake symbols" for multivariate analysis. Is there any functionality in Desktop that might accomplish this or a similar visualization?

Source: Slocum, T. A., McMaster, R. B., Kessler, F. C. and Howard, H. H. 2005. Thematic Cartography and Geographic Visualization, Prentice‐Hall. 2nd edition (p. 355)

Re: Would like to create star and snowflake symbols

DanPatterson_Retired — Wed, 28 Oct 2015 23:38:47 GMT

No but easy to replicate using python and matplotlib there are variants by name and specifics (aka radar, star)

api example code: radar_chart.py — Matplotlib 1.4.3 documentation in essence, you need magnitude and direction data and in your case, you join the points on the outer bounds rather than back to the center.

Be careful about the term star graph, since it also comes from a portion of graph theory, which probably isn't what you want... Star Graph -- from Wolfram MathWorld

Besides their snowflake is so lame, you can expand to variants raspberrypilearning/turtle-snowflakes · GitHub or even take it into fractal space

Some sample data would be useful

Re: Would like to create star and snowflake symbols

DarrenWiens2 — Sat, 11 Dec 2021 14:26:25 GMT

Here's how you can do it with arcpy geometries (10.1+):

>>> fc = "grid" # input feature layer
... sr = arcpy.Describe(fc).spatialReference # spatial ref
... points = []
... lines = []
... polys = []
... fields = ["SHAPE@","var1","var2","var3","var4","var5","var6","var7","var8"] # geometry plus 8 variables
... maxDist = 5 # value multiplier
... with arcpy.da.SearchCursor(fc,fields,spatial_reference=sr) as cursor: # loop through features
...     for row in cursor: 
...         centre = row[0].centroid # centre point
...         newPolyPoints = []
...         for i in range(1,9): # loop through variables
...             x = centre.X + math.cos(math.radians(i*45))*row*maxDist # x offset
...             y = centre.Y + math.sin(math.radians(i*45))*row*maxDist # y offset
...             newPoint = arcpy.PointGeometry(arcpy.Point(x,y),sr) # create point geometry
...             points.append(newPoint)
...             newLine = arcpy.Polyline(arcpy.Array([centre,newPoint.centroid]),sr) # make ray lines
...             lines.append(newLine)
...             newPolyPoints.append(newPoint.centroid)
...         newPoly = arcpy.Polygon(arcpy.Array(newPolyPoints),sr) # make snowflake polygon
...         polys.append(newPoly)
... arcpy.CopyFeatures_management(points,r'in_memory\points') # write points
... arcpy.CopyFeatures_management(lines,r'in_memory\lines') # write lines
... arcpy.CopyFeatures_management(polys,r'in_memory\polys') # write polygons

Re: Would like to create star and snowflake symbols

DanPatterson_Retired — Thu, 29 Oct 2015 19:13:09 GMT

Nice!!! remember this one next time someone asks a boring buffer question

Re: Would like to create star and snowflake symbols

SteveCline — Sun, 08 Nov 2015 14:18:29 GMT

Thank you. That is exactly what I need to do.