I've been using the R package 'survival' recently.
I understand the way to read the survival curves is given time X what is the percent of widgets still in the field Y. And I can get a confidence interval around Y.
But I've been asked if I can go the other way around. Given a percent still in field Y, can I get a time X (and a confidence interval around X) that matches?
I'm looking for either a function in the R package 'survival', or the theory behind generating this.