Extract

1
Extract!

• Powerful but fraught with Booby Traps!

2
What is Extract

• EXTRACT extracts summary statistics from an
  existing image file
• Stand alone - to a on screen tabulation or to an
  attribute values file.
• Modeler only to an attribute values file
• The two input files are,
• an image file and a
• feature definition file.
• The summary statistics are
• minimum, range,
• maximum, average
• total, standard deviation
• of all cells in the analyzed image for each
  identifier in the feature definition image.

3
What is Extract

• EXTRACT extracts summary statistics from an
  existing image file
• Stand alone - to a on screen tabulation or to an
  attribute values file.
• Modeler only to an attribute values file
• The two input files are,
• an image file and a
• feature definition file.
• The summary statistics are
• minimum, range,
• maximum, average
• total, standard deviation
• of all cells in the analyzed image for each
  identifier in the feature definition image.

The feature definition file is an image defining
distinct features or regions. This image must
have byte or integer data type.
4
How does it work?
Extract

• Min
• 3
• 3

• Max
• 4
• 4

• Ave
• 3.5
• 3.5

• Total cells
• 700
• 700

Results
5
How does it work?
Extract
700?
100 Cells at 3 100 Cells at 4 200 Cells at 3.5
700!

• Min
• 3
• 3

• Max
• 4
• 4

• Ave
• 3.5
• 3.5

• Total cells
• 700
• 700

Results
6
How does it work?
Extract

• Min
• 3
• 3

• Max
• 4
• 4

• Ave
• 3.5
• 3.5

• Total cells
• 700
• 700

7
In IDRISI
3
1
2
4
8
In Exercise 6

• The new aspect of the selection process in
  criteria 2 and 4
• 2 -- Have some portion of the parcel within 300
  feet of a road
• Any Ideas?

9
The solution
Have to come to class to find out!
10
Max
Sum
Ave
Parcel
Min
Range
13 0 1 18
0.6428571 1 0.4791574
0.48795 14 0 1
63 0.3705882 1 0.4829623
0.4843891 15 0 1
2 0.08695652 1
0.2817713 0.2881041 16 0
1 33 0.3586957
1 0.4796176 0.4822457 17
0 1 26 0.325
1 0.4683748 0.4713299 18
0 1 2
0.01388889 1 0.1170299
0.1174383 19 0 1
4 0.5 1
0.5 0.5345225 20 1
1 4 1
0 0 0 21
0 1 4
0.6666667 1 0.4714045
0.5163978 22 0 0
0 0 0
0 0 23 0
1 16 0.069869 1
0.2549261 0.2554845 24 0
1 55 0.2619048
1 0.4396711 0.4407217 25
0 0 0 0
0 0 0 26
0 1 45 0.3040541
1 0.4600056 0.4615676 27
0 1 8
0.1052632 1 0.3068922
0.3089314 28 0 1
2 0.6666667 1
0.4714045 0.5773503 29 1
1 2 1
0 0 0 30
1 1 1 1
0 0 0 31
0 0 0 0
0 0 0 32
0 1 2
0.6666667 1 0.4714045
0.5773503
11
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12
Another Trick

• Use the Feature properties function

13
How was that done?

• You have to create the Collection with the
  Collection tool (3rd from right)

14
In the pick list
Have to use these for the trick to work
15
Now the Query works on all layers in the
collection