Re: Some way to differentiate (1st order derivative)?

[<pl...@pi...>]

Delta y / Delta x =3D y(row+1)-y(row)/(x(row+1)-x(row)).

sorry I did reply to this one but it went to Levente only not the list.

this sort of trivial task lends itself nicely to the new assign feature =
 =

(only in CVS AFAIK) and is exactly the sort of thing I had in mind when =
I  =

requested it.

check out the syntax since it is still being developed and may change.

It does not enable you to look ahead or backwards in the data but settin=
g  =

a variables like last_x last_y and diffing to the previous point rather =
 =

than the next will do this nicely.

This can be done inline in the plot command or via a function call in th=
e  =

plot command , that keeps the plot line less cluttered.

Here's two examples: sample max x and y values in plot range and  =

trapezoidal integration area under graph. Again check syntax since I thi=
nk  =

it has changed since I built this CVS snapshot.

xmax=3D0;ymax=3D0;
max(x,y)=3Dassign("ymax",(ymax<y)?y+0. * assign("xmax",x):ymax );


started=3D0;
add_aug(x,y)=3Dassign("area",(started>0)?\
                                       area + (x-prev_x)*(y+prev_y)/2.0 =
 =

+ 0.0*(assign("prev_x",x) \
                                       +assign("prev_y",y) ) \
                                     :  0.0*( assign("started",1)  =

+ assign("prev_x",x) + assign("prev_y",y) ) \
                    ) ;

this using clause is in my plot command:
    using 1:(add_aug( ($1),($2) ))

HTH, Peter.