These functions extract, and plot, the spatially-varying value
of the likelihood ratio test statistic which forms the basis of
the scan test.

If the test result `X`

was based on circles of
the same radius `r`

, then `as.im(X)`

is a pixel image
of the likelihood ratio test statistic as a function of the
position of the centre of the circle.

If the test result `X`

was based on circles of
several different radii `r`

, then `as.im(X)`

is a pixel image
of the profile (maximum value over all radii `r`

)
likelihood ratio test statistic as a function of the
position of the centre of the circle, and
`as.im(X, what="radius")`

is a pixel image giving
for each location \(u\) the value of `r`

which maximised
the likelihood ratio test statistic at that location.

The `plot`

method plots the corresponding image.