# How to assign a unique Value for cells

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6
10-25-2011 08:49 AM
Occasional Contributor
Hi..I wanted to assign a unique value (number) for each cell in the grid..I just wonder if any one can help me ..For my knowledge ArcMap 10 has no such tool, and I guess the only way to do it is through python programming..That is my thought, I may be wrong, don't know..Appreciate if some one can help me out..
Thanks a lot...
Tags (3)
6 Replies
MVP Emeritus
Below provides some food for thought, please consult the appropriate help topics for other options.

```>>> import numpy as np
>>> unique = np.arange(100)
>>> unique = unique.reshape(10,10)
>>> unique
array([[ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9],
[10, 11, 12, 13, 14, 15, 16, 17, 18, 19],
[20, 21, 22, 23, 24, 25, 26, 27, 28, 29],
[30, 31, 32, 33, 34, 35, 36, 37, 38, 39],
[40, 41, 42, 43, 44, 45, 46, 47, 48, 49],
[50, 51, 52, 53, 54, 55, 56, 57, 58, 59],
[60, 61, 62, 63, 64, 65, 66, 67, 68, 69],
[70, 71, 72, 73, 74, 75, 76, 77, 78, 79],
[80, 81, 82, 83, 84, 85, 86, 87, 88, 89],
[90, 91, 92, 93, 94, 95, 96, 97, 98, 99]])
>>> import arcpy
>>> out_raster = arcpy.NumPyArrayToRaster(unique)
>>> out_raster.save("c:/temp/testRaster")
>>>
```
Occasional Contributor
Thanks Dan..Let me give it a try and see, I never used Python before..??
Occasional Contributor III
A non-Python way is to create a fishnet exactly the same as the grid you want: same extents, same cell size.
Build polygons from the fishnet lines
The polygons will all have unique feature ids.
convert the field of little square polygons to a raster with cells the same size as your little squares, using the (unique) feature ids as the value.
by
Occasional Contributor III
Hi,

Similar to the fishnet...this requires the correct tool (spatial analyst?) licenses but is very straight forward.

Use Raster to point tool - creates a point theme with a value field from the raster (These values I assume you do not require)

Then calculate a unique ID field in this dataset using field calculater --> FID / ObjectID

Finally, Point to Raster tool - select your uniqueID values field instead of the original value field.

Done.

Then
Occasional Contributor
Thanks all of you for your contributions..Appreciated..
by
New Contributor
Hi..I wanted to assign a unique value (number) for each cell in the grid..I just wonder if any one can help me ..For my knowledge ArcMap 10 has no such tool, and I guess the only way to do it is through python programming..That is my thought, I may be wrong, don't know..Appreciate if some one can help me out..
Thanks a lot...

Hi mykotti,

I'm looking for simple examples of using numpy for GIS and this seems like a good one -- except I don't really can't guess (or conjure) a reason for creating a raster with a unique value for each cell.  Could you explain?  Thanks.  -- LT