R shiny slider increments -

trying setup slider bar range 0.5 - 999.5 increments of 1 such range of values can take on 0.5, 1.5, 2.5 ... 999.5 . problem when use the slider code below, values including whole integer 1, 2, 3, 4...etc have tried changing steps 0.5 get, 1, 1.5, 2, 2.5 ...etc. ideas?

column(4,          fileinput("pbs", label = ("pbs file input")),          sliderinput("size",                       label = ("size range selection"),                       min = 0.5,                       max = 999.5,                       value = c(0.5,999.5),                      step = 1,                     round = f           ) 

so not greatest, work:

in ui:

  sliderinput("size",                       label = ("size range selection"),                       min = 0,                       max = 999,                       value = c(0,999),                      step = 1,                     round = f,                     post=".5"          ) 

this show slider goes 0 999, adds ".5" labels 0.5 999.5.

then, in server, have add .5 each of values slider before using numbers.