Hi! I have a large dataset where I need to recompute a value in each row based on z-sores from another look-up table. The look-up table is arranged by raw score in the first column and age in the first row, eg: 20 30 40 1 .3 .5 .7 2 .2 .3 .4 3 .1 .4 .7 the main matrix will have ages and raw scores and I need to select the appropriate value from the look-up table. Unfortunately, the distribution of the look-up does not fit a linear model, so I can't compute from a formula. Any suggestions would be appreciated. Thanks Jon -- View this message in context: http://r.789695.n4.nabble.com/change-matrix-based-on-look-up-value-from-table-tp3078870p3078870.html Sent from the R help mailing list archive at Nabble.com.