HeatMap function not working....how can I create a heat map in matlab

I have a time series of volatility factor returns data for about 55 different countries. I want to do some sort of heat map/clustering to group different countries together based on their volatility returns. HeatMap in "undefined for argument double." Let me know if you know any good functions! Or if you think a heat map is the wrong way to go alltogether, perhaps you could suggest a good clustering algorithm for time series data.