Do an interpolation in matlab

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klipya
klipya 2012-7-30
Hi,
I'm newbie in Matlab and I'm trying to do an interpolation but it doesn't work ("The values of X should be distinct.") I don't know exactly what's wrong.
load doc_1.txt
x= doc_1(:,2);
y= doc_2(:,3);
z= 399.25:1:2179.5;
yi= interp1(x,y,z);
plot(x,y,'o',z,yi)
Thanks in advance,
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klipya
klipya 2012-8-6
Thanks Andrei. Interpolation works well, thank you. It's not that what I want. I have a lot of values like 352.4, 352.5 354.3... and I want to get, with the interpolation, only one value from every number. Is that possible?
For example, for the value 352 I want to get one number.

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回答（2 个）

Titus Edelhofer
Titus Edelhofer 2012-8-6
Hi,
you will need to average all values between 352 and 353. To this end use histc to find those effiently and then loop. Here ist the code (only for interval [352 - 353]), the more general should then be not too difficult:
x = [351 351.5 352.2 352.3 353.5 354.5];
y = rand(size(x));
edges = 350:355;
[n,bin] = histc(x, edges);
% for the 352 average on all values between 352 and 354
x352 = x(bin==3)
% x352 is just for illustration, what you need is y352:
y352 = mean(y(bin==3))
Titus
Andrei Bobrov
Andrei Bobrov 2012-8-6
编辑：Andrei Bobrov 2012-8-6
variant
X = [352.4, 352.5 354.3;0.5050,2.4874,1]';
[xa,~,c]=unique(fix(X(:,1)));
Xout = [xa,accumarray(c,X(:,2),[],@mean)];

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