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saving values without index

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zozo
zozo 2012-3-1
%***question updated***%
I have the following situation:-
for d=1:numel(Time_delay) % time delay is (8x1000) matrix
if rem(d,8)==0;
mic_out(1,:)=mic_in(1,:);
out(rem(d,8)+1,:)=sum(mic_out,1);
y=sum(out.^2,2);
mic_out=zeros(size(mic_out));
end
mic_out(rem(d,8)+1,:)= del(mic_in(rem(d,8)+1,:),fs,Time_delay(d+1),2000); %here 'del' is a function which delays the 8 signals in 'mic_in(8x10000)' according to delays specified in Time_delay'
end
The first row in Time_delay is all zeros. So, there is no delay applied. Hence, I replace it with 1st row of signal that is, mic_in(1,10000). Each time I change column in Time_delay, I need to add the 8 delayed signals in mic_out row-wise,square it and add them colum wise(i.e. calculate energy) and store only the energy value and move on.
Then repeat the above process for all columns of Time_delay.
At the end I need only 'y' matrix containing the energies.
Whats the most efficient way to achive this? Please help

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回答（2 个）

Matt Tearle
Matt Tearle 2012-3-1
Why do you not want to use an index? It is less efficient to just append values to an existing array, but you can:
x = [];
for k = 1:5
x = [x,k^2];
end
or even x(end+1) = ...
If the values are of different types or dimensions, use a cell array -- e.g.:
x = {};
for k = ...
x{end+1} = ... % or x = [x,...];
end
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zozo
zozo 2012-3-1
@walter: Please check the above question(updated).

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Walter Roberson
Walter Roberson 2012-3-1
Using the index "end+1" is often clearer coding. It is not clear why indexing should be avoided.
But anyhow, the following technically does not use any indexing:
results = [];
for K = 1 : 20
newvalue = rand(); %whatever the new value should be
results = [results; newvalue]; %add it to the end
end
This is not efficient (before R2011a anyhow.)

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