# Interpolating a non-continuous set of points [closed]

I'm trying to create a pure function that I can feed into OutputResponse[ ] as the input u[t]. In order to do this, I've written code to create a square wave pulse train in the form of a collection of (x,y) points. This is created from two lists: a list of y values ("vVect") and a list of x values ("tVect"). In trying to use Interpolation[ ] (and ListInterpolation[ ]), I am getting back functions that behave different than the set of points they interpolate. Is this just a problem with Mathematica's plotting function? What I want is something that looks exactly like the ListLinePlot, but that I can assign to the function u, as I can't pass a set of points to OutputResponse[ ].

pTrain = Partition[Riffle[tVect, vVect], 2];
ListLinePlot[pTrain]


u = ListInterpolation[vVect, {{0, 0.002}}, InterpolationOrder -> 0]
Plot[u[t], {t, 0, 0.002}]


## closed as off-topic by m_goldberg, Feyre, Wjx, MarcoB, gwrSep 8 '16 at 6:59

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "This question arises due to a simple mistake such as a trivial syntax error, incorrect capitalization, spelling mistake, or other typographical error and is unlikely to help any future visitors, or else it is easily found in the documentation." – m_goldberg, Feyre, Wjx, gwr
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• Please provide at a manageable portion of tVect and cVect, so that your computations can be reproduced. – bbgodfrey Mar 5 '15 at 21:17
• Sorry! tVect:<dropbox.com/s/2pqygz5sfc030o1/tVect.dat?dl=0> vVect: <dropbox.com/s/7nuws5kusoxaxrn/vVect.dat?dl=0> – everson Mar 5 '15 at 21:31

## 1 Answer

You just need more PlotPoints:

tVect = Get["tVect.dat"] ;
vVect = Get["vVect.dat"] ;
pTrain = Partition[Riffle[tVect, vVect], 2];
f = Interpolation[pTrain, InterpolationOrder -> 0] ;
Plot[f[s], Evaluate[Join[{s}, First[f["Domain"]]]], PlotPoints -> 200]