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考虑一个数字向量， a <- c(75,26,65,27,97,72)

和一个矩阵 10x6 矩阵 b

1.4168709   0.6253624   2.08645202  2.9475645   1.29317931  0.80175442
0.3669328   0.851852    0.57428245  2.8542504   1.40075478  0.01745655
6.1173956   1.6848444   1.05468424  0.3382552   1.1428774   0.41141215
2.8203602   0.9573334   0.22131122  0.4406137   0.07209113  0.17910147
0.102152    0.1779387   0.94915127  0.3516491   1.48272109  0.06037996
0.3124434   0.4892484   2.04443039  0.1251463   2.41507973  1.25367433
0.2154152   0.3951161   0.60410084  0.7551265   0.55764737  1.17793564
1.5451135   0.7764766   3.11515773  1.3519765   0.08916275  1.39969422
0.4018092   0.2432501   0.06470464  2.6173665   0.24696145  5.27272096
1.1683212   0.1258633   0.19431636  0.4160356   1.61775945  0.78849181

输入

b <- structure(c(1.41687091749774, 0.366932780481875, 6.11739562418232, 
2.8203601760972, 0.102152034174651, 0.312443420290947, 0.215415194164962, 
1.54511345728281, 0.401809234172106, 1.16832122397808, 0.625362366437912, 
0.851851973640633, 1.68484436153414, 0.957333435262454, 0.177938693314666, 
0.489248352590948, 0.395116138737649, 0.776476616387118, 0.243250062223524, 
0.125863284132781, 2.08645202020619, 0.57428245106712, 1.05468423915856, 
0.221311220899224, 0.949151266561806, 2.04443038991633, 0.604100843891501, 
3.11515773070936, 0.0647046443940286, 0.194316359037562, 2.94756450172152, 
2.85425036383753, 0.338255227074493, 0.440613748457464, 0.351649099495262, 
0.125146273523569, 0.755126529331219, 1.35197646259786, 2.61736654663894, 
0.416035552509129, 1.29317931454153, 1.40075477585735, 1.14287740174205, 
0.072091125883162, 1.48272109049815, 2.41507973323081, 0.557647368015562, 
0.0891627511009574, 0.246961451135576, 1.61775945491138, 0.80175441955164, 
0.0174565480835137, 0.411412146408111, 0.179101474117488, 0.0603799588836676, 
1.25367433010839, 1.17793564121695, 1.39969422101023, 5.27272095591089, 
0.788491813423944), .Dim = c(10L, 6L))

我的问题是如何将向量 a 与矩阵 b 逐行相乘。我知道b%*%a会做什么。

我正在尝试做这样的事情

75*1.4168709 + 26*0.6253624 + 65*2.08645202 + 27*2.9475645 + 97*1.29317931 + 72*0.80175442

75*0.3669328 + 26*0.851852 + 65*0.57428245 + 27*2.8542504 + 97*1.40075478 +     72*0.01745655

很快

任何建议都非常感谢。

4

2 回答 2

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我们可以在进行乘法之前获得相同的长度，即通过复制“a”元素

a[col(b)] * b
#          [,1]      [,2]       [,3]      [,4]       [,5]       [,6]
# [1,] 106.265319 16.259422 135.619381 79.584242 125.438394  57.726318
# [2,]  27.519959 22.148151  37.328359 77.064760 135.873213   1.256871
# [3,] 458.804672 43.805953  68.554476  9.132891 110.859108  29.621675
# [4,] 211.527013 24.890669  14.385229 11.896571   6.992839  12.895306
# [5,]   7.661403  4.626406  61.694832  9.494526 143.823946   4.347357
# [6,]  23.433257 12.720457 132.887975  3.378949 234.262734  90.264552
# [7,]  16.156140 10.273020  39.266555 20.388416  54.091795  84.811366
# [8,] 115.883509 20.188392 202.485252 36.503364   8.648787 100.777984
# [9,]  30.135693  6.324502   4.205802 70.668897  23.955261 379.635909
#[10,]  87.624092  3.272445  12.630563 11.232960 156.922667  56.771411

或转置'b'，然后乘以'a'并转置输出

t(t(b) * a)
#          [,1]      [,2]       [,3]      [,4]       [,5]       [,6]
# [1,] 106.265319 16.259422 135.619381 79.584242 125.438394  57.726318
# [2,]  27.519959 22.148151  37.328359 77.064760 135.873213   1.256871
# [3,] 458.804672 43.805953  68.554476  9.132891 110.859108  29.621675
# [4,] 211.527013 24.890669  14.385229 11.896571   6.992839  12.895306
# [5,]   7.661403  4.626406  61.694832  9.494526 143.823946   4.347357
# [6,]  23.433257 12.720457 132.887975  3.378949 234.262734  90.264552
# [7,]  16.156140 10.273020  39.266555 20.388416  54.091795  84.811366
# [8,] 115.883509 20.188392 202.485252 36.503364   8.648787 100.777984
# [9,]  30.135693  6.324502   4.205802 70.668897  23.955261 379.635909
#[10,]  87.624092  3.272445  12.630563 11.232960 156.922667  56.771411

或者rep更明确地使用rep

rep(a, each = nrow(b)) * b
#           [,1]      [,2]       [,3]      [,4]       [,5]       [,6]
# [1,] 106.265319 16.259422 135.619381 79.584242 125.438394  57.726318
# [2,]  27.519959 22.148151  37.328359 77.064760 135.873213   1.256871
# [3,] 458.804672 43.805953  68.554476  9.132891 110.859108  29.621675
# [4,] 211.527013 24.890669  14.385229 11.896571   6.992839  12.895306
# [5,]   7.661403  4.626406  61.694832  9.494526 143.823946   4.347357
# [6,]  23.433257 12.720457 132.887975  3.378949 234.262734  90.264552
# [7,]  16.156140 10.273020  39.266555 20.388416  54.091795  84.811366
# [8,] 115.883509 20.188392 202.485252 36.503364   8.648787 100.777984
# [9,]  30.135693  6.324502   4.205802 70.668897  23.955261 379.635909
#[10,]  87.624092  3.272445  12.630563 11.232960 156.922667  56.771411

或者我们可以split将矩阵“b”按列转换为 a list，并将其与mapply. 现在，相应的单个单位相乘

mapply(`*`, split(b, col(b)), a)

一旦，我们完成了上述步骤，就做rowSums

out2 <- rowSums(a[col(b)] * b)
out2
#[1] 520.8931 301.1913 720.7788 282.5876 231.6485 496.9479 224.9873 484.4873 514.9261 328.4541

- 使用 OP 的方法检查输出

out1 <- (b%*%a)[,1]
out1
#[1] 520.8931 301.1913 720.7788 282.5876 231.6485 496.9479 224.9873 484.4873 514.9261 328.4541
all.equal(out1, out2)
#[1] TRUE
于 2018-11-22T19:06:00.223 回答
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看起来像一个sweep- 操作。在适用于边距的函数的 R 中，“2”通常表示列操作，从您的参数和结构来看，我将如何描述您的预期结果。n（我可以看到您如何将其称为“逐行”，但大多数 R 用户会认为这是应用“逐列：。

> sweep(b,2,a,"*")
            [,1]      [,2]       [,3]      [,4]       [,5]       [,6]
 [1,] 106.265319 16.259422 135.619381 79.584242 125.438394  57.726318
 [2,]  27.519959 22.148151  37.328359 77.064760 135.873213   1.256871
 [3,] 458.804672 43.805953  68.554476  9.132891 110.859108  29.621675
 [4,] 211.527013 24.890669  14.385229 11.896571   6.992839  12.895306
 [5,]   7.661403  4.626406  61.694832  9.494526 143.823946   4.347357
 [6,]  23.433257 12.720457 132.887975  3.378949 234.262734  90.264552
 [7,]  16.156140 10.273020  39.266555 20.388416  54.091795  84.811366
 [8,] 115.883509 20.188392 202.485252 36.503364   8.648787 100.777984
 [9,]  30.135693  6.324502   4.205802 70.668897  23.955261 379.635909
[10,]  87.624092  3.272445  12.630563 11.232960 156.922667  56.771411

然后只是rowSums：

> rowSums( sweep(b,2,a,"*") )
 [1] 520.8931 301.1913 720.7788 282.5876 231.6485 496.9479 224.9873 484.4873 514.9261 328.4541

或者，矩阵运算：

  a %*% t(b)
         [,1]     [,2]     [,3]     [,4]     [,5]     [,6]     [,7]     [,8]     [,9]    [,10]
[1,] 520.8931 301.1913 720.7788 282.5876 231.6485 496.9479 224.9873 484.4873 514.9261 328.4541

以及稍快的单功能版本：

tcrossprod(a,b)
         [,1]     [,2]     [,3]     [,4]     [,5]     [,6]     [,7]     [,8]     [,9]    [,10]
[1,] 520.8931 301.1913 720.7788 282.5876 231.6485 496.9479 224.9873 484.4873 514.9261 328.4541
于 2018-11-22T19:34:46.887 回答