Function to lookup values according to an index. Aims to behave similarly to VLOOKUP in Microsoft Excel, however several lookups can be made at once (indexval can be a vector) and interpolation is available where lookups are inexact (choice of 4 methods).
Arguments
- indexval
The index value to be looked-up (may be a vector of multiple values)
- indexvec
The vector of indices to look-up within
- valvec
The vector of values corresponding to the vector of indices
- method
Method may be
floor,ceiling,arithorgeom(default).
Value
Numeric value or vector, depending on the lookup/interpolation method chosen:
floor: Floor (minimum) value, where interpolation is required between measured valuesceiling: Ceiling (maximum) value, where interpolation is required between measured valuesarith: Arithmetic mean, where interpolation is required between measured valuesgeom: Geometric mean, where interpolation is required between measured values
See also
HMDHFDplus::readHMDweb can be used to obtain lifetables from the Human Mortality Database
Examples
# Suppose we have survival probabilities at times 0 to 20
times <- 0:20
survival <- 1-times*0.04
# We would like to look-up the survival probability at time 7
vlookup(7, times, survival)
#> [1] 0.72
# In this case, the floor, ceiling, arith and geom values are identical
# because survival time 7 is known, and no interpolation is necessary
vlookup(c(7, 7.5), times, survival)
#> [1] 0.7200000 0.6997142
# The second row of the returned tibble reveal different estimates of the survival at time 7.5.
# The values vary according to the interpolation method between
# observed survival values at times 7 and 8.