       Re: Having some trouble with plot and solve

• To: mathgroup at smc.vnet.net
• Subject: [mg115529] Re: Having some trouble with plot and solve
• From: Alexei Boulbitch <alexei.boulbitch at iee.lu>
• Date: Thu, 13 Jan 2011 03:29:51 -0500 (EST)

```Hi,
you may go the following way. Copy the code below to the Input cell of your notebook and execute it.
Epsilon is the value you are looking for.

data = {{0, .005}, {100, .00465}, {200, .00432}, {400, .00374}, {600, \
.00323}, {900, .00260}, {1200, .00209}, {1500, .00168}};

(* Here the data is logarithmed and the new list contains the pairs (t, Log[c]): *)
Clear[g];
g[{x_, y_}] := {x, Log[y]};
dataLog = Map[g, data]

(* Here we fit the logarithmed data *)
ftLog = Fit[dataLog, {1, t}, t]
\[Epsilon] = Abs[ftLog[[2, 1]]]

(* The following 3 operations are only to visualize the result and get roughly an impression,
if the fit we have found indeed fits. *)
lstLogPl =
ListPlot[dataLog, PlotStyle ->  Red,
AxesLabel ->  {Style["t", 16, Italic], Style["ln(c)", 16, Italic]}];

ftLogPl = Plot[ftLog, {t, 0, 1500}];

Show[{lstLogPl, ftLogPl}]

Have fun, Alexei

Hi i am new to mathematica, i have tried to combine this simple
problem of showing a Reaction speed but i cannot plot the tangent line
on a plot, and i don't seem to be able to have my regression in the
same notebook

data = {{0, .005}, {100, .00465}, {200, .00432}, {400, .00374}, {600,
\
.00323}, {900, .00260}, {1200, .00209}, {1500, .00168}};
N2O5 = Exp[Fit[data /. {x_, y_} ->  {x, Log[y]}, {1, x}, x]] //
Simplify (*not in same notebook as the rest*)

f[x_] := 0.00499929 E^(-0.000726892 x) (*this works*)
g=B4[x_] := -3.63394*10^-6 E^(-0.000726892 x) (*this works*)

Plot[0.00499929 E^(-0.000726892 b), {b, 0, 4000},
PlotRange ->  {0, .006}](*this works*)

Show[Plot[0.00499929 E^(-0.000726892 x), {x, -1000, 4000}],
ListPlot[data, PlotRange ->  {0, .006}, PlotStyle ->  {Red}]] (*this
works*)

Manipulate[
Solve[g=B4[x0]*{x - x0} + f[x0] == y], {x0, 0, 1500, 1, Appearance ->
"Labeled"}] (*this works*)

But i cannot combine it together, not even this small thing
Manipulate[
Plot[y /. Solve[g\.b4[x0]*{x - x0} + f[x0] == y], {x0, 0, 1500, 1,
Appearance ->  "Labeled"}], {x, 0, 4000}, PlotRange ->  {0, .006}]

--
Alexei Boulbitch, Dr. habil.
Senior Scientist
Material Development

IEE S.A.
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