Returning Jenks or CartoCSS value?

[Randy Brown]

Is there a way to query and return the Jenks bin values?  Or is there a way to query and return the full set of CartoCSS values for a specific table?

I need to be able to dynamically set the CSS used for display when building maps from 3 separate fields.  Each field creates a unique set of Jenks bins.  I either need to know what those are (dynamically) or what the CartoCSS that is generated for those bins.

The documentation shows info on Jenks (SELECT CDB_JenksBins(array_agg(numeric), integer)), but I'm not sure that the API includes access.

Thanks.


Randy

[Florian Lengyel]

I'm interested in this as well. 

I'd like to use the CSS generated by the cartodb classifications (Jenks, Equal Value, Quantiles, Long Tail) to set the colors of  histograms bins for histograms generated by user selected points on a map. (I'm generating the histograms and know what the bins are.)  I'd also like to use the CSS to dynamically generate legends. The histogram data is generated by a REST endpoint (for now, until the river network and sampled data is in PostGIS/CartoDB and is queryable from there) based on a user selection. 

Developers seem to be on their own when it comes to synchronized interactive displays of legends and histograms. Desktop GIS systems can handle this. The web seems to present an opportunity for development.

Thanks!

F Lengyel

gmail/skype/twitter florianlengyel

Randy

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[Andrew Hill]

Hey Randy,

The Jenks bins are calculated by a special function we have here,

https://github.com/CartoDB/cartodb20/wiki/CartoDB-PLpgSQL

You can read the description and use the function in an SQL whenever you like. The only thing is that when we run it through the UI for you, we supply the data as a SELECT * FROM table WHERE column != NULL; like we talked about in the other thread.

So on your table, to get the same result as the UI go,

SELECT CDB_JenksBins(array_agg(column_name::numeric), 7) FROM table_name WHERE column_name IS NOT NULL; 

or something close to that...

Cheers,

a

Randy

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www.vizzuality.com | @andrewxhill

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[carvingcode]

Cool.  Will give it a go.

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[Javier Santana]

If you are interested the code that generates the sql query is here:

https://github.com/CartoDB/cartodb20/blob/develop/lib/assets/javascripts/cartodb/models/table.js#L1313

we are working on 2.1 release right now, i think the next improvement in the UI will be the legends, so any feedback would be really appreciated

www.cartodb.com

[carvingcode]

Thanks for the link.  I will dig in.

Regarding legends:

- Allow for specifying textual labeling within legend.

- Allow for CSS control of the legend, i.e.: vertical, horizontal, top, left, right, bottom, etc.

Thanks.

Randy

[carvingcode]

Javier -

Without locking you to a deadline, do you anticipate legend support in the next few months, end of year...?

Randy

On Wed, Jun 26, 2013 at 2:34 AM, Javier Santana <jsan...@vizzuality.com> wrote:

[Javier Santana]

thanks for your feedback.

the plan is:

- release cartodb 2.1 with multilayer support in the following weeks

- after that we will work on legends, so I suppose it will be ready within 3 months 

[carvingcode]

Andrew - What do I actually pass into the 'array_agg(numeric)' parameter?  I did some tests, entering the column name and numeric position.  The first returns an error.  The second returns a break scale of [null,6,6,6,6].

What is the actual data you need passed into  'array_agg(numeric)'?

Thanks.

Randy

On Tue, Jun 25, 2013 at 2:14 PM, Andrew Hill <and...@vizzuality.com> wrote:

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[carvingcode]

Nice!

[Andrew Hill]

Hi Randy,

You pass it the column name (numeric type), so in the email I sent you before, I ensured that I cast it with, array_agg(column_name::numeric).

Cheers,

a

[carvingcode]

Awesome!  Got it!

[carvingcode]

For what it's worth, here's a Javascript function that will return the Jenks bins values.  It currently displays to the console, but can easily be modified for specific use.

    function getJenksBins(column_name, how_many_bins, table_name) {

        var sql = new cartodb.SQL({ user: 'cartodb_user' });

        sql.execute('select CDB_JenksBins(array_agg(' + column_name + '::numeric), ' + how_many_bins + ') from ' + table_name + ' where ' + column_name + ' is not null')

                .done(function (data) {

                    console.log(data.rows[0].cdb_jenksbins[0]);

                    console.log(data.rows[0].cdb_jenksbins[1]);

                    console.log(data.rows[0].cdb_jenksbins[2]);

                    console.log(data.rows[0].cdb_jenksbins[3]);

                    console.log(data.rows[0].cdb_jenksbins[4]);

                })

                .error(function (errors) {

                    // errors contains a list of errors

                    console.log("error:" + err);

                })

    }

    window.onload = getJenksBins("the_column", 5, "the_table");