What are histograms and how do they work in regards to filter.

[dbauszus-glx]

A histogram is a graphical representation of numerical data that groups the data into ranges (bins) and displays the frequency of each range as a bar.

A filter histogram is associated with the distribution of that field. In this example the histogram shows the distribution of population per square meter.

I might be interested in specific subset of locations. eg. areas with more than 100000 population. Hence I must be able to enter a filter value manually.

I may interested in a very small subset on the range eg 100000 to 200000.

Transforming the size of the histogram element does not add information.

Histogram are designed to show the distribution of individual filter fields. In this example I set the minimum range for population density to 100000, and then minimum count for juveniles to 100. Each histogram shows the distribution of the areas with the associated field being used for the histgram query. Both filters are applied. The distribution of locations with a juvenile count of more than a hundred only takes into account areas with a population density of more than 100000.

Here are the same histograms with the population density condition reset.

The linear range slider can not easily be associated with non linear bins that are dependent on other factors [other field filter and the viewport].

One possible approach could be to make the histogram clickable. Take the bin with highest distribution for example.

If I set the min/max of the bin on the filter you will see how small the linear range is. This can not work with steps.

[cityremade]

so at the moment this is unclear that the histogram visualises the filtered subset as it is not related to the range set on the dual filter - it stretches along the full input width. What do we do to make this distinct?
And yes, some people don't know how to use histogram so we want to make it readable for them.

[dbauszus-glx]

There is a bug for dynamic histograms in regards to the viewport not being applied. #2282

There is also a bug in regards to no data being returned when multiple filter are used. #2278

Once these bugs are resolved we can also think about static histograms. A static histogram will always show the same distribution for the total dataset. This will not work for huge datasets but smaller datasets. In a static histogram we can display the range of the current filter by colouring the histogram bars that are within the range.

A static histogram will not be updated with other filters.