在R中叠加10个密度图，其颜色与重叠图的数量成比例

I have a dataset with 224900 observations and 10 variables which are the result of different Taylor series back transformations to original data values. I wish to overlay the density plots of each of these 10 variables to show the level of robustness of the Taylor series back transformation on the data estimates. Rather than having just 10 lines, I thought it would be good to have a colour apply, so that each density plot contributes 10% of a grey scale. Where there is data that just relates to one of the plots, there would be 10% grey, two plots would be twice as dark at 20%, up to where all the density plots overlap, which would be 100%.I have a dataset with 224900 observations and 1