CustomColorFunction, color classes & legend

[sylvaincaillot]

Good morning,
First of all congratulations for this amazing plugin.

I am developing a map with a chloropeth layer similar to you countystats example.
I would like to give the user the posiibility to choose its color palette(sequential/diverging) and the number of data classes as in the Colorbrewer website.
Using this webpage and this site (http://www.cse.unsw.edu.au/~mike/myrlibrary.old/RColorBrewer/html/ColorBrewer.html), i have been writing the following code for sequential and diverging colors:

var fillColorSeq = new L.CustomColorFunction(range[0], range[1], L.ColorBrewer.Sequential.PuBuGn['9']);
var fillColorDiv= new L.CustomColorFunction(range[0], range[1], L.ColorBrewer.Diverging.PRGn['11']);

I works OK but when i reduce the number of color classes (eg.:L.ColorBrewer.Diverging.PRGn['4']);), i would expect to have 4 colors only in my map and legend but, i still continue to have more colors than data classes with perhaps a clearer tint.

Am i doing something wrong?
Should i use the slice attribute? I didn't find much information on it.

At least, is it possible to define automatically the number of segments of the legend based on the number of data classes chosen for the customeColorFunction without using the numSegments option of the legend and the gradient effect?
I would like to get something similar to the Colorbrewer site.

Thanks in advance for your reply.

Sylvain

[sfairgrieve]

Sylvain,

Good question. You can pass an interpolate option in the
L.CustomColorFunction constructor like so:

var fillColorSeq = new L.CustomColorFunction(range[0], range[1],
L.ColorBrewer.Sequential.PuBuGn['9'], {
    interpolate: false
});

This will ensure that only the 9 or 4 or desired number of color classes
are used rather than interpolating between colors.

As far as the legend goes, it looks like that's a bug or at least an
oversight. The legend will always use a gradient, even if it doesn't make
sense (as in this case). I will push a fix in the next few days that makes
this configurable. Thanks for pointing this out.

Thanks,

Scott

Sent from my iPhone

On Mar 21, 2014, at 6:52 PM, sylvaincaillot notifications@github.com
wrote:

Good morning,
First of all congratulations for this amazing plugin.

I am developing a map with a chloropeth layer similar to you countystats
example.
I would like to give the user the posiibility to choose its color
palette(sequential/diverging) and the number of data classes as in the
Colorbrewer website.
Using this webpage and this site (
http://www.cse.unsw.edu.au/~mike/myrlibrary.old/RColorBrewer/html/ColorBrewer.html),
i have been writing the following code for sequential and diverging colors:

var fillColorSeq = new L.CustomColorFunction(range[0], range[1],
L.ColorBrewer.Sequential.PuBuGn['9']);
var fillColorDiv= new L.CustomColorFunction(range[0], range[1],
L.ColorBrewer.Diverging.PRGn['11']);

I works OK but when i reduce the number of color classes
(eg.:L.ColorBrewer.Diverging.PRGn['4']);), i would expect to have 4 colors
only in my map and legend but, i still continue to have more colors than
data classes with perhaps a clearer tint.

Am i doing something wrong?
Should i use the slice attribute? I didn't find much information on it.

At least, is it possible to define automatically the number of segments of
the legend based on the number of data classes chosen for the
customeColorFunction without using the numSegments option of the legend and
the gradient effect?
I would like to get something similar to the Colorbrewer site.

Thanks in advance for your reply.

Sylvain

Reply to this email directly or view it on
GitHubhttps://github.com//issues/25
.

[sfairgrieve]

Just pushed an update which should make this work. In the DataLayer legendOptions section, just include an option called gradient with a value of false in addition to setting interpolate to false in the L.CustomColorFunction. I updated the county stats example to illustrate this.

[sylvaincaillot]

It works beautifully. Thanks for your prompt answer.
Is there a way to reset LegendOptions where the numSegments has changed for example. I tried to look for something similar to setDisplayOptions for legendOptions but didn't find anything.

Sylvain