Not sure how to do a smoothing average of noisy data

Question

Jason 2015-2-19

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https://ww2.mathworks.cn/matlabcentral/answers/179164-not-sure-how-to-do-a-smoothing-average-of-noisy-data

评论： Jason 2015-2-19

采纳的回答： Image Analyst

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Not sure how to do a smoothing average of noisy data based off what the instructions asked this is what I've come up with so far any help would be appreciated.

clear;
clc;
load('noisydata.mat','x');
N = x;
y = zeros(1,length(N));
for k = 2:1:length(x)
    if (k~= 1 & k~= N)
        y(k) = (x(k-1)+x(k+1))/2;
    end 
end

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Answer 1

Image Analyst 2015-2-19

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You forgot to set y(1) = x(1) before the loop, and, after the loop, set y(length(x)) = x(end). Then have your loop go from k = 2 : (length(x)-1).

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Image Analyst 2015-2-19

编辑：Image Analyst 2015-2-19

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Well I said to put y(length(x))= x(end); after the loop, not inside it.

And for some reason you plotted only a single point

plot(y(k))

instead of the whole curve:

plot(x, 'r*-');
hold on;
plot(y, 'b-', 'LineWidth', 2);

But anyway, try that, because other than that it looks like it should work. But you didn't attach noisydata.mat so I can't test it.

Jason 2015-2-19

sorry about that I thought I did just attach it to this comment. I really appreciate the help to! thank you. The reason I plotted only one point was I because I wasn't sure what to compare the noisy data with, and what to compare the smoothed data with.

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Answer 2

Geoff Hayes 2015-2-19

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Jason - I think that you have correctly interpreted what the question is asking (less the plot) but you may want to reconsider the condition for your if statement

if (k~= 1 & k~= N)

Remember that k is a scalar but N is a vector/array so this comparison is not what you want. If you want to exclude the first and last elements from x then just extend what you have started with the for statement

for k = 2:1:length(x)-1

So now k ranges from 2 to one less than the length of x which is exactly which values you need to consider (and so no longer have any need for the condition).

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Geoff Hayes 2015-2-19

Jason - you are being asked to plot the original noisy data versus the sample number. The sample numbers are the indices into your noisy matrix x. How would you plot this?

Jason 2015-2-19