The Heat Map output of Create Expression Plot

In a Heat Map each row corresponds to a gene and each column to a cell. The color in the $ i$'th row and $ j$'th column reflects the expression level of feature $ i$ in cell $ j$ (the color scale can be set in the Side Panel). The expression values used are z-score normalized for each gene. This allows the relative expression of genes with very different average expressions to be visualized in the same plot, but means that expression values cannot be compared between genes - only between cells for the same gene.

There are a number of options to change the appearance of the Heat Map. At the top of the Side Panel, you find the Heat Map group (see figure 9.2).

Image heatmap
Figure 9.2: A heat map visualization of data from [MacParland et al., 2018].

Below you find the Cells and Features groups. They contain options to show names, color legends, and, in the case of Features, trees at the left or right of the heat map. The tree options also control the Tree size, including the option of showing the full tree, no matter how much space it will use.

The Metadata group makes it possible to visualize all the information in the Cell Clusters and Cell Annotations supplied when the Heat Map was created: