ggsave保存图片报错Error in x$theme : $ operator not defined for this S4 class

p=Heatmap(as.matrix(expr))
ggsave(file="test.png",p)
Saving 0.884 x 0.836 in image
Error in x$theme : $ operator not defined for this S4 class

解决方法：用png()保存即可

png(file="test_infercnv.png")
Heatmap(as.matrix(expr)）
dev.off()