Interpolation points for determining values in between known data points
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In this function, i want to use interp1 to generate a linear, cubic, and spline interpolation among points in the above sequence. The x values to be interpolated are x2interp = 1:0.1:10. I want to assign the resulting arrays of linear cubic, and spline interpolated values to y1, y2, and y3, respectively. Then plot the 3 dierent interpolations along with the original data on a single gure. (for the graph I am providing a legend to indicate the type of interpolation that each curve represents. blue circles to represent original data, red dashed line for linear interpolation, green dotted line for cubic interpolation and black solid line for spline interpolation.)
The set of data is :
x 1 2 3 4 5 6 7 8 9 10
y -2 3 -4 6 -7 10 -17 25 -26 30
I think I know the basic idea on how to write a interpolation function, but how do I incorporate the above data into my function?
function [y1, y2, y3] = MyInterpolator()
interp1 = interp1(X,Y,Xi)
yI = interp1(X,Y,Xi,'linear')
Y2 = interp1(X,Y,Xi,'cubic')
Y3 = interp1(X,Y,Xi,'spline')
PP = spline(X,Y)
x2interp = 1:0.1:10
ylabel('y')
xlabel('x')
legend('original data','linar','cubic', 'spline')
lines = {'original data','linar','cubic', 'spline'}
legend(lines)
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Accepted Answer
Star Strider
on 26 Oct 2012
Edited: Star Strider
on 26 Oct 2012
You're almost there! If you want to pass the x, y, and x2interp to your MyInterpolator function, I suggest changing the first line to:
function [y1, y2, y3] = MyInterpolator(X, Y, Xi)
then call it as:
[y1, y2, y3] = MyInterpolator(x, y, x2interp)
I also mention that you need to correct some typos so that your code reads:
y1 = interp1(X,Y,Xi,'linear')
y2 = interp1(X,Y,Xi,'cubic')
y3 = interp1(X,Y,Xi,'spline')
MATLAB is case-sensitive, so Y1 is not the same as y1.
Please eliminate this line:
interp1 = interp1(X,Y,Xi)
You redefine interp1 with it as a variable rather than a function and the following three lines will throw an error because of that.
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More Answers (1)
Azzi Abdelmalek
on 26 Oct 2012
Edited: Azzi Abdelmalek
on 26 Oct 2012
function [y1, y2, y3] = MyInterpolator()
x =[ 1 2 3 4 5 6 7 8 9 10]
y=[ -2 3 -4 6 -7 10 -17 25 -26 30]
plot(x,y,'ob')
xi=1:0.1:10
method=char('linear','cubic','spline')
col={'--r',':g','-k'}
for k=1:3
yi{k}=interp1(x,y,xi,method(k,:))
hold on;plot(xi,yi{k},col{k})
end
y1=yi{1}
y2=yi{2}
y3=yi{3}
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