### MATLAB >> linear spline - 1st order

Hi

I am using the spline command to fit some data. However, I would like
to know if I can specify the order of the polynomial function of each
segment.

I want to use only the 1st order, i.e. linear spline.

now i used

model = spline( ytraX, xtraX );

but how i can specify the order to be 1.

thanks

```Dear Matlab users,

Does anyone know how to solve the following ODE numerically in Matlab?

u(x)*(du/dx) = -p(x) -D*u(x)^2

with the boundary condition

u(infinity)=1

and p(x) known.

I have tried bvp4c, but without success. I don't know what to do with
the u(x)*(du/dx) term. One can solve the equation analytically but I
must solve some parts numerically anyway, so I thought I could solve the
whole thing numerically.

Regards

Daniel Soderstrom
```

```Hello,
I would plot this nonlinear differential equation :

RC * dy/dt + y(t) = x(t);
x(t) = sin(wt);

If I consider R=cste there is non problem and I can plot the
solution quickly but in reality I would have :

R = 1 / ( x(t) * ( 1-exp( -sqrt(x(t)) ) ) / sqrt(x(t) )

Matlab can't solve it, it run and never finish the calcul.
Even if I use a simple form for R=1/(x(t) * 0.9);
Someone could tell me how to solve this equation ?
thanks

PS : this is what I've done :
I've use the ode45 solver

%In Matlab
tspan = [1e-9 1e-6];
y0 = 0;
[t, y] = ode45('dydt',tspan,y0);
plot(t, y);

%%% The function I've define in a dydt.m file
function dydt = dydt(t, y)
w=2*pi*1e6;
x = sin(wt);
C = 10e-15;
R = 1 / (0.9*x(t));
dydt = 1/(R*C) * (x - y);
%end of function
```

```Hello all,

In the documentation of the Matlab PDE Toolbox, the problems that can
be solved by using PDE are described as 2nd order PDE problems, i.e.
elliptic parabolic problems.

I have a 1st order PDE problem with one spatial dimension and time
variable. Can I solve that problem with PDE toolbox as well.

Specifically my problem is solving the equations of unsteady flow of
a gas inside a tube. Therefore, I also have two time and distance
dependent temperatures, namely gas temperature and wall temperature.

Sahina
```

```I have a set of points (x_1,y_1),(x_2,y_2)...(x_n,y_n)
I am trying to find a "cubic spline" 'interpolating' (passing thru)
these points. It should start from the first point and stop at the
last point.

Is there a fast way to do this in matlab?  I looked at the
spline toolbox but most examples there are for
single valued functions.

Thanks,
--j

```