# PDE Toolbox solution array along a line, to then find the mean value

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A on 29 Jan 2015
Commented: Bill Greene on 31 Jan 2015
I'm have solved Poisson's equation for simple rectangular geometry using the PDE Toolbox. I exported the solution and mesh and now I want to find u along a line so that I can then find its average.
It is a rectangle with bottom boundary at y = -0.8 and x = -0.5 to 0.4. This is what I was trying to type in the command line:
F = pdeInterpolant(p,t,u);
x = -0.5:0.4;
y = -0.8;
uOut = evaluate(F,x,y)
But this only returns one value. I am looking for an array of values so that I can use mean(uOut) to find the average.
I also want to find the the mean normal component of u into the page at the same position.
Any help greatly appreciated.

Bill Greene on 29 Jan 2015
The evaluate function is returning only one value because the length of your x and y vectors is one. Maybe you want something like this:
F = pdeInterpolant(p,t,u);
n = 10;
x = linspace(-.5,.4,n);
y(1:n) = -.8;
uOut = evaluate(F,x,y)
to interpolate along the line between x=-.5 and x=.4
##### 2 CommentsShowHide 1 older comment
Bill Greene on 31 Jan 2015
PDE Toolbox is 2D only so it's functions won't be helpful in calculating a gradient in the z-direction.

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