You probably also want to do something like
P=plot_slope_field(-g,(x,0,3),(y,0,20))
since the slope of the solution is -g, not g.
-Marshall
On Nov 30, 4:37 pm, Jason Grout <jason-s...@creativetrax.com> wrote:
> kcrisman wrote:
> > Dear support,
>
> > I'm giving a talk Wednesday and would like to do the following
> > interact as an example of how easy interacts are:
>
> > y = var('y')
> > @interact
> > def _(g=input_box(default = 1-y)):
> > P=plot_slope_field(g,(x,0,3),(y,0,20))
> > y = function('y',x)
> > f = desolve(diff(y,x) + g, y, ics=[2,2])
> > Q=plot(f,0,3)
> > show(P+Q)
>
> > Only it isn't easy. The declaring of y = function('y',x), which is
> > necessary to use desolve, causes the following error:
>
> > UnboundLocalError: local variable 'y' referenced before assignment
>
> > And the 'g' in the desolve also causes problems shortly thereafter. I
> > tried a lot of things to fix this, but nothing seemed to work quite
> > right. Note that this works nicely without interact.
>
> > Any help one can give in a relatively timely basis would be much
> > appreciated! Thanks in advance,
>
> It looks like you are confusing y-as-a-variable and y-as-a-function an
> awful lot. How about:
>
> y = var('y')
> @interact
> def _(g=input_box(default = 1-y)):
> P=plot_slope_field(g,(x,0,3),(y,0,20))
> yfun = function('yfun',x)
> f = desolve(diff(yfun,x) + g(y=yfun), yfun, ics=[2,2])
> Q=plot(f,0,3)
> show(P+Q)
>
> Does that give what you want?
>
> Jason
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