Merging a bar chart with a map

Seamlessly merge a bar chart with a map to display geographically-coded categorical variables

Let us break down the example code that calls the bar_chart function:

1. Data Loading:

• The code begins by loading data from a file named dataexample.

1. Data Description:

• The following variables are described:
• Idx: Index of data. This could be countries, provinces, etc.
• BoundingBox: Maximum and minimum latitude and longitude values.
• Lon and Lat: Vertices defining the boundaries of the map object. These can be obtained from loading a .SHP object and extracting the vertices.
• centerLon and centerLat: By default, the center of BoundingBox, but this can be any coordinates that the user requires.
• The column titles VarX_categY are the Yth category of variable X.

1. Selecting Data to Plot:

• The code defines sets of indices (idxtoplot{n}) to select the specific columns of the data table for plotting.
• These indices correspond to the columns containing data to be plotted on the bar chart.

1. Creating Useful Things:

• The colormap for the bars is set using Colors=colormap('Lines'), but any type of color map can be used.

1. Merging Geographical Map and Bar Chart:

• The barchart_map function is called with the loaded data (dataexample), selected indices (idxtoplot), and options (optionsfig).
• The resulting figure handle (h) and other relevant elements (hmap and hdata) are stored.

1. Aesthetics and Annotations:

• After the graph is generated, the user can tweak and add various objects by making explicit references to the graph objects.

Now let us dive into the plotting function barchart_map.

The function called barchart_map generates a graph combining geographical limits with a bar chart.

1. Inputs:

• data: A table containing the data.
• idxtoplot: A cell array specifying the columns of data to be plotted.
• options: A structure collecting various plot options.

1. Options:

• The function checks if options is provided. If not, default values are set:
• options.factorLon: Shrinkage factor for the width of the bars.
• options.factorLat: Shrinkage factor for the height of the bars.
• options.offsetLon: Spacing between bars.
• options.newfigure: Determines whether a new figure needs to be generated.
• options.Colors: Colormap for the bars.

1. Data Processing:

• The function processes the data and organizes it into YData for plotting.

1. Plotting:

• It plots the geographical map using plot(data.Lon{i,1}, data.Lat{i,1}).
• For each data point, it creates stacked bars based on the specified columns and their values.

1. Outputs:

• out: Figure handle.
• outmap: Elements corresponding to the map.
• outdata: Elements corresponding to the data bars.