Thanks for reply Zelgar but I'm still looking for help, sorry, probably because I haven't explained problem accurately or clearly. Therefore I attach file showing the specific problem. There are 2 charts both with curves from same data (see data!). One is correct, the other is wrong.
The...
To get horizontal/vertical (example) line touch at a user-defined point on a linear curved line (not trendline), I've tried:
Equation: y = m * x + b
m: =SLOPE(y,x)
b: =INTERCEPT(y,x)
and
=INDEX(LINEST,y,x,cond)
on y,x ranges -- see attached file
but the only way I can...
