Re: Mass 'identify' on 2d-plot

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Re: Mass 'identify' on 2d-plot

Evgeniy Kachalin
Barry Rowlingson пишет:

> Evgeniy Kachalin wrote:
>
>> What is ability in R to graphically (per mouse) define some area and
>> to select all the cases felt in it?
>>
>> 'identify' is OK for 5-10 cases, but what if cases=1000?
>
>
>  You can use 'locator' to let the user click a number of points to
> define a polygon, and then use one of the point-in-polygon functions
> provided by one of the spatial packages to work out whats in your polygon.
>
>  Look at splancs, spatstat, sp - pretty much anything beginning with
> 'sp' - on CRAN.
>
>  In splancs you can just do:
>
>  poly = getpoly()
>
>  - which lets the user draw a polygon on screen, then:
>
>  inPoly = inpip(xypts,poly)
>  points(xypts[inpip,], pch=19,col="red")
>
>  and that will plot the selected points in solid red dots.
>
>  I don't think there's a way to draw a freehand figure on an R plot, you
> have to go click, click, click, and draw straight lines.
>

I don't get what is 'xypts' in this case... One step earlier i've
plotted plot(y~x,data=dat). What is xypts?

--
Evgeniy Kachalin

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