Do an interpolation in matlab

2012 7 30
2 个回答
7 次查看（30 天）

0 个投票

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,

4 个评论
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Oleg Komarov
Oleg Komarov 2012-7-30
I assume "The values of X should be distinct" is an error. As it says, your x values should all be different.
klipya
klipya 2012-7-30
编辑：Andrei Bobrov 2012-7-30
Thanks Oleg, I will apply some function to erase them or I will erase it directly. One other question. I have different values like:
X Y
352.4 0.5050
352.5 2.4874
Is there any possibility to get only one value for 352, for example? Thanks a lot!
Andrei Bobrov
Andrei Bobrov 2012-7-30
interp1(X,Y,352,'linear','extrap')
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

0 个投票

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

0 个投票

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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klipya
klipya
2012-7-30

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