Error using griddedInterpolant. The grid vectors must contain unique points

Hi All,

Trying to plot two different datasets with a uniform x-axis I ran through a loess filter. My code for the interp/plotting worked on one dataset, but not on another. Can't seem to figure out the issue here.

The one that worked:

% Interpolation Method 
% y1 = first dataset 
% yn = nth dataset 
% yn = interp1(x,y,std x component,'[insert optional interp method]') 
% repeat for nth datasets

y1 = interp1(x87Age,y87C,t_comp87); 
y2 = interp1(x41Age,y41C,t_comp41);

plot(x87Age,y87C,'o'); 
hold on 
plot(x41Age,y41C,'o'); 
plot(t_comp87,y1); 
plot(t_comp41,y2);

The one that didn't work

% Interpolation Method 
% y1 = first dataset 
% yn = nth dataset 
% yn = interp1(x,y,std x component,'[insert optional interp method]') 
% repeat for nth datasets

y1 = interp1(x87Age,y87C,t_comp87); 
y2 = interp1(x79Age,y79C,t_comp79);

plot(x87Age,y87C,'o'); 
hold on 
plot(x79Age,y79C,'o'); 
plot(t_comp87,y1); 
plot(t_comp79,y2);

Any ideas???

Answer 1

[Ankitha Kollegal Arjun]

This error generally occurs when there are duplicate points in the input to 'interp1'.

You can remove duplicates using 'unique' function.

For Example,

[x, index] = unique(x); 
yi = interp1(x, y(index), xi);

Please apply the above logic to your code and see if it resolves the issue.

[Vince Clementi]

Thanks! Found the dupes.

[Jacob Bradshaw]

What does "index" here mean?

[Jacob Bradshaw]

wait... got it. This fuction is sick. B-)

[lakshman s]

Suppose there are 2 points of Y for 1 value of x. Then how to get the value of both the data points? No point is duplicate for me.

[Cyril Besson]

Thank you, I works very well.