[R] Spatstat - Several density plots using the same scale

[Rolf Turner]

On 10/10/2008, at 4:48 AM, Arthur Weiss wrote:

> Hi everyone,
>
> I am using the package "spatstat" for ploting kernel maps of my data.
> It is a marked point pattern, the result of mosquito surveillance in a
> area in a week.
> For each trap, the number of individuals captured is the mark of  
> the point.
>
>> plot(density(X, weights=X$marks))
>
> makes a nice kernel, but the problem is that I've got several weeks  
> and
> for each week the density is re-scaled, which makes comparisons  
> useless.
> I've been trying to find some way to pass the scale limits to the  
> function
> but just couldn't find.

Not quite sure what the problem is ... but the help for plot.im() says:

				.
				.
				.

           numeric-valued images: By default, the range of pixel  
values in
           'x' is divided into 'n = length(col)' equal subintervals,
           which are mapped to the colours in 'col'. (If 'col' was not
           specified, it defaults to a vector of 255 colours.)

           Alternatively if the argument 'zlim' is given, it should be a
           vector of length 2 specifying an interval of real numbers.
           This interval will be used instead of the range of pixel
           values. The interval from 'zlim[1]' to 'zlim[2]' will be
           mapped to the colours in 'col'. This facility enables the
           user to plot several images using a consistent colour map.

Does setting the zlim argument accomplish what you want?  If not, please
get back to us with more detail.

	cheers,

		Rolf Turner

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