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POWays to quickly update an element of a matrix in Incanter, Clojure?
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copied!<p>Suppose I have a 3x3 matrix </p> <pre><code>(def myMatrix (matrix (range 9) 3)) ; A 3x3 matrix ; ------------- ; 0.00e+00 1.00e+00 2.00e+00 ; 3.00e+00 4.00e+00 5.00e+00 ; 6.00e+00 7.00e+00 8.00e+00 </code></pre> <p>I can use $ to get an element, say 2nd row 1st column </p> <pre><code>($ 1 0 myMatrix) ; --> 3 </code></pre> <p>Is there any API method to quickly update an element and then return a matrix? e.g.</p> <pre><code>(update-matrix-by-element 2 1 myMatrix 4) ; A 3x3 matrix ; ------------- ; 0.00e+00 1.00e+00 2.00e+00 ; 4.00e+00 4.00e+00 5.00e+00 ; 6.00e+00 7.00e+00 8.00e+00 </code></pre> <p>The closest API methods I can find are <a href="http://clojuredocs.org/incanter/incanter.core/bind-rows" rel="nofollow">bind-rows</a> and <a href="http://clojuredocs.org/incanter/incanter.core/bind-columns" rel="nofollow">bind-columns</a>, and my current version of function using these two methods is </p> <pre><code>;note i j starts from 1 rather than 0 (defn update-matrix-by-element [i j myMatrix value] (if (or (> i (count (trans myMatrix))) (> j (count myMatrix)) (< i 1) (< j 1) (not (integer? i)) (not (integer? j))) myMatrix (let [n (count myMatrix) m (count (trans myMatrix)) rangeFn #(if (== %1 %2) %1 (range %1 %2 )) m1 (if (== (dec i) 0) [] ($ (rangeFn 0 (dec i)) :all myMatrix)) m2 (if (== i m) [] ($ (rangeFn i m) :all myMatrix)) matrixFn #(if (matrix? % ) % [ %]) newRow (if (== (dec j) 0) (bind-columns [value] (matrixFn ($ (dec i) (rangeFn j n ) myMatrix))) (if (== j n ) (bind-columns (matrixFn ($ (dec i) (rangeFn 0 (dec j) ) myMatrix)) [value] ) (bind-columns (matrixFn ($ (dec i) (rangeFn 0 (dec j) ) myMatrix)) [value] (matrixFn ($ (dec i) (rangeFn j n ) myMatrix)))) ) ] ; (prn " m1 " m1 ) (prn " m2 " m2 ) (prn " newrow " newRow) (bind-rows m1 newRow m2)))) </code></pre>

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