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In Matlab R2010a:

I am familiar with finding values based on criteria as well as finding the first value in a vector that satisfies criteria. However, how does one find X's and not Y's in the following example? In this case, X's are the first values of a group of values that are findable given my criteria, and there are multiple groups like this amidst thousands of junk values.

I have an vector with 10,000 or more values. Let J be junk values, while X and Y are both values my find criteria will pick up. X's are interesting to me because they are the 'first' values of a series of values that satisfy my criteria before becoming J's. Assume that there are hundreds or thousands more J's in between the X's and Y's, but here is a small example

[J,J,J,J,J,J,J,J,J,J,J,X,Y,Y,Y,Y,J,J,J,J,J,J,J,J,J,X,Y,Y,Y,Y,J];
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2 回答 2

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假设你没有对那些Xs 和Ys 做一些奇怪的事情，这很容易。您只需要找到每个集群的开头：

% Create data using your example (Y can equal X, but we make it different)
J = 1; X = 2; Y = 3;
A = [J,J,J,J,J,J,J,J,J,J,J,X,Y,Y,Y,Y,J,J,J,J,J,J,J,J,J,X,Y,Y,Y,Y,J];

a0 = (A==X);                      % Logical indices of A that match X condition
start = find([a0(1) diff(a0)]==1) % Start index of each group beginning with X
vals = A(start)                   % Should all be equal to X

返回

start =

     12    26


vals =

      2     2

这些J值甚至不需要完全相同，只是不等于您检测到的值X。您可能还会发现我对这个类似问题的回答很有帮助。

于 2013-08-06T21:42:24.127 回答
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A = [J,J,J,J,J,J,J,J,J,J,J,X,Y,Y,Y,Y,J,J,J,J,J,J,J,J,J,X,Y,Y,Y,Y,J]; % created vector
I = A(A~=J); % separated out all values that are not junk
V = I(I==I(1)); % separated all values that match the first non-junk value
于 2013-08-06T21:39:30.150 回答