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lijunjiexm鐵蟲 (小有名氣)
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[求助]
求助一簡單matlab程序的出錯問題,謝謝
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如下m文件,為什么在命令窗口運行 出現(xiàn)錯誤提示: >> A=mesh2d2(10) ??? Index exceeds matrix dimensions. Error in ==> mesh2d2 at 8 A = sparse (ii(keep), jj(keep), xx(keep)); >> 請大家指點,謝謝! %%%%%%%%%%%%%%%%%%%%%%% function A = mesh2d2 (n) % create an n-by-n 2D mesh for the 2nd difference operator nn = 1:n^2 ; ii = [nn-n ; nn-1 ; nn ; nn+1 ; nn+n] ; jj = repmat (nn, 5, 1) ; xx = repmat ([-1 -14-1-1]',1, n^2) ; keep = find (ii >= 1 & ii <= n^2 & jj >= 1 & jj <= n^2) ; A = sparse (ii(keep), jj(keep), xx(keep)); |
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把最后一行“A = sparse (ii(keep), jj(keep), xx(keep)); ”轉換成 A = sparse (ii(keep)); A = sparse (jj(keep)); A = sparse (xx(keep)); 再試試看。sparse函數(shù)轉化只能一個個來吧。 另外,你xx = repmat ([-1 -14-1-1]',1, n^2) ;是想生成2*100個元素的矩陣,不過按照你的程序應該生成5*100矩陣吧。猜測而已。[-1 -14-1-1]應為[-1 -1 4 -1 -1]吧?? |

至尊木蟲 (著名寫手)
驃騎將軍

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function A = mesh2d2 (n) % create an n-by-n 2D mesh for the 2nd difference operator nn = 1:n^2 ; ii = [nn-n ; nn-1 ; nn ; nn+1 ; nn+n] ; jj = repmat (nn, 5, 1) ; xx = repmat ([-1 -14-1-1]',1, n^2) ; [keep1,keep2]= find (ii >= 1 & ii <= n^2 & jj >= 1 & jj <= n^2) ; keep=[keep1 keep2]; % A = sparse (ii(keep), jj(keep), xx(keep)); A1 = sparse (ii(keep)); A2 = sparse (jj(keep)); A3 = sparse (xx(keep)); |

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