Usage
    heatmap_grob(data, signed = TRUE, legend_title = "", vp_name = NULL, to = NULL)
 
    
    Arguments
- data
- Matrix of data to display. 
- signed
- Should a signed palette be used? 
- legend_title
- Title for legend grob. 
- vp_name
- Viewport name for heatmap grob. This is useful if you will need to refer to the grob later, for example for interaction. 
- to
- Heatmap scale will include this value if given. 
 
    
    Value
    A list containing a heatmap grob and associated legend grob.