I'm trying to decide on the classification method: natural breaks, equal interval, quantiles, or manual and the number of classes for a map showing the mean temperature of places in Canada.
The values range from -20 degrees to 10 degrees. The mean is -2 and the median is -1.7.
I'm not sure what to consider when deciding these things. The higher the number of classes, the better it seems to look, but it's hard to decide on the number of classes that is most useful to viewers of the map.