Maps are powerful because they help you gain a deeper understanding of your data by allowing you to visualize it in many ways. For example, population data for countries can be visualized as a sequence of colors, such as from light to dark, or as graduated circles, such as from small to large. This flexibility allows you to tell different stories and discover hidden patterns depending on how the data is presented. But because mapmaking is flexible, it requires you to make decisions when there isn't always a single best answer.
Fortunately, for any given data or layer, ArcGIS for Power BI allows you to explore styling options using smart mapping defaults.
The map themes that are available when you click Symbology are determined by the data you're mapping. For example, you'll see different themes if your map layer is composed of points rather than boundary locations. The available themes are also determined by the type of data associated with the locations in the layer. For example, a point may have location information such as geographic coordinates but may also have categorical information such as retail location type, or numerical information such as sales details. Not every map theme can be used for every data type. By analyzing these and other characteristics of your layer, ArcGIS for Power BI presents the available styling choices.
Note:
You can change the symbology for data layers only. You cannot change the symbology for reference layers.
To change the map theme, complete the following steps:
- Open a map-enabled report or create a new one. If necessary, place the report in Author mode.
- In the Layers list, click Layer options
on the data layer you want to modify and choose Symbology 
.Tip:
The Symbology option appears only on layers created using Power BI data.
The Symbology pane appears, listing available map theme options based on the nature of the layer's data.
- Hover over the Information button
to view a brief description of the theme. Click a map theme to select it.The map automatically displays the new theme.
Map themes
The map themes in ArcGIS for Power BI are described below.
Location Only
Style location data using a single symbol. This theme shows each location on the map using the same symbol.
Heat Map
You can use heat maps to visualize the density of points on a map. Heat maps are useful when many of the points on the map are close together or overlapping, making it difficult to distinguish between locations. They are also effective for displaying layers that contain a large number of points.
Heat maps use the points in the layer to calculate and display the relative density of points on the map as smoothly varying sets of colors ranging from cool (low density of points) to hot (many points). It's best to avoid heat maps if you have only a few locations; instead, map the actual points.
Optionally, drag a numerical value into the Size field well to better define the heat map properties.
Note:
Tooltips are not available in heat map layers.
Also, because a heat map uses a specified color ramp to render point density, a value placed in the Color field well is ignored.
Size
This map theme uses graduated symbol sizes to represent your numerical data or ranked categories, allowing you to visually compare quantities and identify trends. In these proportional symbol maps, larger symbols represent larger numbers. Adjust the size of the symbols to clarify the story you're telling. For example, you can use graduated symbols to show store revenue. Add a numerical field value to the map visualization's Size field well to enable this theme.
If your mapped locations are represented by polygons and you place a numeric value in the Size field well, the map updates to show graduated symbols, with the symbol placed in the center of the area defined by the original polygon.
Color
If your data is numeric, you may want to distinguish map locations based on a color ramp. Different types of color ramps can be used. For example, a simple light-to-dark color ramp is good for showing low-to-high data values such as age, income, or ratio. Color ramps like this can be applied to points or boundaries. For example, you can use a light-to-dark color ramp to show store profits.
If you have categorical data, you can style locations by specifying different colors for each category. Add a field value to the map visualization's Color field well to enable this theme.
Size & Color
With this theme, you choose two field values in your data and finalize both the size and the color of point symbols on your map. Or, you can use the same field twice: to set the size of the symbols, and to set the colors, based on the part of the data you want to emphasize. When you have numeric data, this is a good style to use to show count information, such as the number of female single-parent households, shaded by a rate.
To style your map by size and category, drag a categorical data field into the Color field well.
You can also use this style if your data contains date values that you want to show sequentially as a continuous timeline on the map along with another field. If you add a date field value to the Color field well, color is used to show the date values, while proportional symbols are used to show the value in the Size field well. If you place the date value in the Size field well, the reverse is true: dates are shown using proportional symbols and color is used to show the other field value.