MATLAB示例(3)

3 6 9 A =

1 4 7 2 5 8 3 6 9 10 11 12 A =

1 4 7 10 2 5 8 20 3 6 9 30 10 11 12 40

1.4.7 矩阵收缩

A = reshape(1:16,4,4) A(2,:) = []%删除第2行 A(:,3) = []%再删除第3列 A =

1 5 9 13 2 6 10 14 3 7 11 15 4 8 12 16 A =

1 5 9 13 3 7 11 15 4 8 12 16 A =

1 5 13 3 7 15 4 8 16

1.4.8 矩阵复制

A = reshape(1:4,2,2) B = repmat(A,2,3) A =

1 3 2 4 B =

1 3 1 3 1 3 2 4 2 4 2 4 1 3 1 3 1 3 2 4 2 4 2 4

1.5 简单数据处理

1.5.1 元素的和与积

x = 1:10

y = reshape(1:9,3,3) a = sum(x)

b = sum(y)%对每一列求和 c = sum(y,2)%对每一行求和 x =

1 2 3 4 5 6 7 8 9 10 y =

1 4 7 2 5 8 3 6 9 a = 55 b =

6 15 24 c = 12 15 18 x = 1:10

y = reshape(1:9,3,3) a = prod(x)

b = prod(y)%对每一列求积 c = prod(y,2)%对每一行求积x =

1 2 3 4 5 6 7 8 9 10

y =

1 4 7 2 5 8 3 6 9 a =

3628800 b =

6 120 504 c = 28 80 162

1.5.2 平均值和中位数

x = [1 2 5 6 7 8 9] y = [1 2 5;2 3 7;6 8 11] a = mean(x)

b = mean(y)%每一列平均值 c = mean(y,2)%每一行平均值 x =

1 2 5 6 7 8 9 y =

1 2 5 2 3 7 6 8 11 a =

5.4286 b =

3.0000 4.3333 7.6667 c =

2.6667 4.0000 8.3333

x = [1 2 5 6 7 8 9] y = [1 2 5;7 8 2;6 3 11] a = median(x)

b = median(y)%每一列的中位值 c = median(y,2)%每一行中位

x =

1 2 5 6 7 8 9 y =

1 2 5 7 8 2 6 3 11 a = 6 b =

6 3 5 c = 2 7 6

1.5.3 最大最小值

x = 1:10

y = reshape(1:9,3,3) a = max(x)%最小值用min b = max(y)%每一列的最大值

c = max(y,[],2)%每一行最大值，空矩阵不能少x =

1 2 3 4 5 6 7 8 9 10 y =

1 4 7 2 5 8 3 6 9 a = 10 b =

3 6 9 c = 7 8 9

1.5.4 累计求和、积

x = [1:3;4:6;8:10]

a = cumsum(x)%累计和；累计求积用cumprod b = cumsum(x,2) x =

1 2 3 4 5 6 8 9 10 a =

1 2 3 5 7 9 13 16 19 b =

1 3 6 4 9 15 8 17 27

1.5.5 矩阵排序

x = [8 2 1;2 8 3;9 1 7] sort(x)

[y,k] = sort(x,2,'descend') x =

8 2 1 2 8 3 9 1 7 ans =

2 1 1 8 2 3 9 8 7 y =

8 2 1 8 3 2 9 7 1 k =

1 2 3

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