I have a regression problem where I want to predict actuals (dependent variable) of some process where I only have values for a small number of independent variables at the beginning of the process but more non missing data as the process matures. This is kind of similar to survival analysis, which I have used in the past, but with left censoring. However, in contrast to survival analysis I want to predict the value of a continuous variable instead of a (survival) probability. Are there specific regression approaches I can use (e.g. truncated regression, censored regression)? Any pointers, especially to R/Python packages, would be very much appreciated. Many thanks!