以递增方式的数据帧的独立行的总和

I have a data.frame that is 100x100 and I need to sum them up as an escalator. Starting with the first entry of the first column and then keep adding the first entry of the second column to the second entry of the first and so on until the the last entry to sum is the last row of the last column. Looking at it as a diagonal matrix such as that is 100x100 and I need