扩展数据框以在ggplot2中绘制热图

I want to generate a heat map from an all-vs-all comparison. I have the data, already scaled to 0-1. However, I have the values only for the comparisons in one way, and not for the comparisons between the same group (which are always 1), i.e. I have half the matrix and am missing the other half and the diagonal. What is a good way to get it into a form that ggplot2 can use for the heat map?I want to generate a heat map from an all-vs-al