How do I pad the middle of an array?

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Amanda Beatty 2021-4-6

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评论： Amanda Beatty 2021-4-9

I have an array that is basically stepped. I want to pad each side of the step with additional numbers (the orange cells). Can you help me figure out how to do this?

Original Array:

How I want it to be:

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Answer 1

DGM 2021-4-7

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For vectors, you can just extrapolate each segment and cat them back together. You'd need to determine where each step is.

a=[1:6 78:82 109:111]'
b=[interp1(a(1:6),1:8,'linear','extrap'), ...
   interp1(a(7:11),-1:7,'linear','extrap'), ...
   interp1(a(12:14),-1:5,'linear','extrap')]'

gives:

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DGM 2021-4-7

编辑：DGM 2021-4-7

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Those second vectors specify the new query points. What's confusing is that the short syntax I used is basically using the vector length as "x" so to speak. So it's like doing this:

interp1(1:5,a(7:11),-1:7,'linear','extrap');

so I'm taking a 5-element vector and I'm extrapolating two elements off of either end.

Yeah, you wouldn't want to do that a bunch of times, but the idea is the same. The only hard part about doing it automatically is determining the criteria you're going to use to detect what you consider to be a step. For this example, I'm just going to assume a maximum difference.

clc
a=[1:6 78:82 109:111]'
ps=2; % specify a padsize
% i'm assuming that any increment >1 is considered a discontinuity
a=reshape(a,[1 numel(a)]); % safeguard against vector orientation
discloc=find(diff(a)>1); % find transitions
discloc=[discloc(1) diff([discloc numel(a)])] % find width of chunks
chunks=mat2cell(a,1,discloc); % split vector into subvectors
for c=1:numel(chunks)
	% you had chunk 1 padded asymmetrically
	% you can also pad the last chunk asymmetrically if you want
	if c==1
		indexvec=1:(numel(chunks{c})+ps);
	else
		indexvec=(1-ps):(numel(chunks{c})+ps);
	end
	chunks{c}=interp1(chunks{c},indexvec,'linear','extrap');
end
b=cell2mat(chunks)'