# Replace.im

##### Reset Values in Subset of Image

Reset the values in a subset of a pixel image.

##### Usage

```
## S3 method for class 'im':
[(x, i) <- value
```

##### Arguments

- x
- A two-dimensional pixel image.
An object of class
`"im"`

. - i
- Object defining the subregion or subset to be extracted.
Either a spatial window (an object of class
`"owin"`

) or a point pattern (an object of class`"ppp"`

) or something that can be converted into a point pattern by - value
- Vector of replacement values (short vectors will be recycled).

##### Details

This function changes some of the pixel values in a
pixel image. The image `X`

must be an object of class
`"im"`

representing a pixel image defined inside a
rectangle in two-dimensional space (see `im.object`

).

The subset to be changed is determined by the argument `i`

.

If `i`

is a spatial window (an object of class `"owin"`

),
the values of the image inside this window are changed.

If `i`

is a point pattern (an object of class
`"ppp"`

, or something that can be converted into a point pattern
by `as.ppp`

), then the values of the pixel image at the points of
this pattern are changed.

If `i`

does not satisfy any of the conditions above,
then it is assumed to be a valid index for
the matrix `as.matrix(x)`

.

##### Value

- The image
`x`

with the values replaced.

##### See Also

##### Examples

```
# make up an image
X <- setcov(unit.square())
plot(X)
# a rectangular subset
W <- owin(c(0,0.5),c(0.2,0.8))
X[W] <- 2
plot(X)
# a polygonal subset
data(letterR)
R <- affine(letterR, diag(c(1,1)/2), c(-2,-0.7))
X[R] <- 3
plot(X)
# a point pattern
P <- rpoispp(20)
X[P] <- 10
plot(X)
# change pixel value at a specific location
X[list(x=0.1,y=0.2)] <- 7
```

*Documentation reproduced from package spatstat, version 1.23-3, License: GPL (>= 2)*