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imported>Scott |
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| ===Purpose===
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| Calculates semivariance for texture analysis.
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| ===Synopsis===
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| :[y,s] = semivar(x,s,options)
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| ===Description===
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| SEMIVAR calculates the semivariance similar to that used in Kriging, and can be used to characterize texture for the input (x) which is an m by n matrix (e.g. an image layer). The (y) a cell with each element containing a vector of the sqrt(semivariance) and (s) a cell with the associated distance vectors (in pixels). Each cell element corresponds to the semivariance calculated for 4 directions
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| * '''y{1},''' s{1} is down the rows (top-to-bottom), | |
| * '''y{2},''' s{2} is down the columns (left-to-right),
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| * '''y{3},''' s{3} is diagonal (upper left-to-bottom right), and
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| * '''y{4},''' s{4} is diagonal (upper right-to-bottom left).
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| The semivariance is defined as:
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| === ===
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| with larger semivariance indicating less correlation.
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| Optional input (s) is a 2 element cell containing the distances (in pixels) measures to be calculated. Each cell contains a vector of integers defining the distance in pixels for the rows and columns respectively. Defaults:
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| * '''s{1}''' = 1:floor(m/2); s{3} = s{1}\*sqrt(2);
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| * '''s{2}''' = 1:floor(n/2); s{4} = s{1}\*sqrt(2);
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| ''options'' is a structure discussed below.
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| ===Options===
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| ''options'' is a structure is a structure array with the following fields:
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| * '''flag''': [ 'off' | {'on'} ] when set to 'off' the function only calculates the first two semivariances (top-to-bottom and left-to-right). This is faster when (x) is large.
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| * '''plots''': [ 'none' | {'final'} ] governs level of plotting,
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| ===See Also===
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| [[anglemt]], [[autocor_img]], [[detrend_img]], [[fft_texture]], [[svd_texture]], [[texture]]
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