Attribute charts
The “Charts” tab displays simple interactive charts (histogram and scatter plot) of the selected attribute, with the data of the currently selected features highlighted in red. The charts can be zoomed in and panned, and the chart re-centred by clicking on the “A” icon on the lower left corner of the chart. The charts also allow the direct selection of values, which is reflected on the map window, on the “Stats” tab, and retained on the chart if another attribute is selected. In the case of the histogram, two vertical yellow lines are used to set a range of values for selection.
In the case of the scatter plot, the dependent variable is set in the “Y axis” drop down menu that contains all the attributes from the list above. With the scatterplot the charts tool also calculates the correlation coefficient (r) and the linear regression of the two variables, displaying the R2 and linear equation. The regression line on the chart can be switched on and off. The points on the scatterplot can be selected by clicking directly on them. The “shift” key is used to add further points to the selection.
Note:
The charts are provided by the excellent pyqtgraph Python package. Currently there is a rendering bug on Mac OSX that can show the histogram selection lines and the regression lines as very thick lines that obscure the chart. This only occurs with some attribute ranges. There is currently no other solution to the problem than switching the auxiliary lines off.