reset data
reset i/o
reset plot control
dimension 500 30
read linewid.dat day position x y
let b0 = 0.2817
let b1 = 0.9767
let s = 0.06826
let df = 38
let alpha = 0.05
let m = 3
let zeta = .5*(1 - exp(ln(1-alpha)/m))
let TSTAR = tppf(zeta, df)
let W = ((y - b0)/b1) - x 
let CENTER = W - W
let LCL = CENTER + s*TSTAR/b1
let UCL = CENTER - s*TSTAR/b1
characters * blank blank blank
lines blank dashed solid solid
y1label control values
xlabel TIME IN DAYS
plot W CENTER UCL LCL vs day
.end of calculations