View source for where

{{DavinciWiki_Function|
Partial replacement for arrays. This is not a function in the normal sense.
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Arguments: A boolean expression involving an array; must be used in conjunction with an array assignment (see below)
 
Return Value: Returns new array
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The unary operator 'where' provides partial array replacement, based on a boolean expression.  The 'where' operator can only be used during array assignment, and only on a named array.

The [[Syntax]] is as follows:

array [ where expr1 ] &#61; expr2

Array is a named array.

Expr1 must evaluate to an array with the same organization and dimensions as array, and where expr1 is true, the corresponding element of array is replaced with the value of expr2.

Expr2 must be a single value.


In typical usage, array[where array ?&#61; value1] &#61; value2

"array" is a named array

"?&#61;" is a boolean operator (e.g. >&#61;)

"value" is the test value (a 1x1x1 array)


Example:
This example replaces all values in data that are less than zero, with the value 0.

 dv> data[ where (data < 0) ] &#61; 0

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 dv> x &#61; create(7) - 3
 7x1x1 array of int, bsq format [28 bytes]
 -3      -2      -1      0       1       2       3
 dv> x[where x<0] &#61; 0
 7x1x1 array of int, bsq format [28 bytes]
 0       0       0       0       1       2       3

 dv> image[where stddev(image) > 3] &#61; 0
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[[category:Functions]]
[[category:Davinci_Core]]
[[category:Miscellaneous]]