### SUB

Subtracts one NDF data structure from another

#### Description:

The routine subtracts one NDF  data structure from another pixel-by-pixel to produce a new NDF.

sub in1 in2 out

#### Parameters:

First NDF, from which the second NDF is to be subtracted.
Second NDF, to be subtracted from the first NDF.
##### OUT = NDF (Write)
Output NDF to contain the difference of the two input NDFs.
The title for the output NDF. A null value will cause the title of the NDF supplied for Parameter IN1 to be used instead. [!]

#### Examples:

sub a b c
This subtracts the NDF called b from the NDF called a, to make the NDF called c. NDF c inherits its title from a.
sub out=c in1=a in2=b title="Background subtracted"
This subtracts the NDF called b from the NDF called a, to make the NDF called c. NDF c has the title "Background subtracted".

#### Notes:

If the two input NDFs have different pixel-index bounds, then they will be trimmed to match before being subtracted. An error will result if they have no pixels in common.