How to get an average of two cells in specific conditions?

Hello,

I'm working with a rather large Excel document that I'm importing into Matlab 2016b (or 2019b as well) and trying to manipulate, the data is degrees of a circle as an array of 960x13.

For example:

x = [ 23.50128 22.0385 18.058

35.71267 25.44106 13.09361

9.335854 218.1108 -0.63557

40.69297 27.41063 -1.69481

27.22272 25.38112 -0.57529 ]

I need to average any number within the array that is greater than 90, or less than -90, with the number above and below it then replace the value that exceeds those parameters. In this example, I need 218.1108 to be instead be replaced with the averave of 25.44106 and 27.41063, the rest being left alone. I'm sure I'll have to use some sort of If statement to specify it but I'm uncertain on how to really get at this. Additionally, I run into the problem that sometimes the number outside of the parameters will be directly followed by another number outside the parameters and should in this case not be averaged with it but with the two numbers directly proceeding or following it. This may be rather complicated, but if anyone has any advice on how to approach this it would be greatly appreciated!

Thank you!

Answer 1

[Marco Riani]

Hi GDT, please let me know if the code below solves your problem.

x = [  23.50128  22.0385  18.058
    35.71267  25.44106  13.09361
    100  218.1108  91
    110  27.41063  92
    27.22272  25.38112  -0.57529 ];
y=x;

% Find the position of the values which have to be replaced
ind2replace=find(abs(x)>90);

% loop over ind2replace
for i=1:length(ind2replace)
    indi=ind2replace(i);
    % Find position of first element smaller than 90 before indi
    posbefore=find(abs(x(1:indi))<90,1,'last');
    % Find position of first element smaller than 90 after indi
    posafter=indi+find(abs(x(indi:end))<90,1,'first')-1;
    % Take the average of x(posbefore) and x(posafter)
    y(indi)=0.5*(x(posbefore)+x(posafter));
end
disp('Before')
disp(x)
disp('After')
disp(y)

Before (x)

23.5013 22.0385 18.0580

35.7127 25.4411 13.0936

100.0000 218.1108 91.0000

110.0000 27.4106 92.0000

27.2227 25.3811 -0.5753

After (y)

23.5013 22.0385 18.0580

35.7127 25.4411 13.0936

31.4677 26.4258 6.2592

31.4677 27.4106 6.2592

27.2227 25.3811 -0.5753

Of course an additional if has to be put if the element to replace is the first or the final one.

Happy new year!

[GDT]

This worked phenomenally, thank you so much!

Answer 2

[David Hill]

You could try something like:

a=find(x>90|x<-90);
for i=1:length(a)
    x(a(i))=mean(x([a(i)-1,a(i)+1]));
end