继续上题，为了程序编写简洁，要给数据框x中的6列重新命名为x1,x2,x3,x4,x5,x6,应该使用的命令是（）
A: ColNames(x) <- c("x1","x2","x3","x4","x5","x6")
B: Names(x) <- c("x1","x2","x3","x4","x5","x6")
C: colnames(x) <- c("x1","x2","x3","x4","x5","x6")
D: colname(x) <- c("x1","x2","x3","x4","x5","x6")
A: ColNames(x) <- c("x1","x2","x3","x4","x5","x6")
B: Names(x) <- c("x1","x2","x3","x4","x5","x6")
C: colnames(x) <- c("x1","x2","x3","x4","x5","x6")
D: colname(x) <- c("x1","x2","x3","x4","x5","x6")
举一反三
- 假设有一幅4列4行的数字图像（左图），邻域窗口大小为3列3行，经多样性统计之后，右图中的B应分别为何值：2 5 3 4 x x x x4 3 1 2 x x B x6 7 5 3 x x x x1 3 5 4 x x x x A: 3 B: 4 C: 5 D: 6
- 已知数据x1，x2，x3，x4，x5的平均数为a，则数据4x1，4x2，4x3，4x4，4x5的平均数为______；4x1-2，4x2-2，4x3-2，4x4-2，4x5-2的平均数为______．
- 求函数 f(x)=3*x1^2 + 2*x1*x2 + x2^2 − 4*x1 + 5*x2. 时,输入代码 >>fun = @(x)3*x(1)^2 + 2*x(1)*x(2) + x(2)^2 - 4*x(1) + 5*x(2); >>x0 = [1,1]; >>[x,fval] = fminunc(fun,x0); 其中fun的作用是:
- 设函数f(x)=(x2-6x+c1)(x2-6x+c2)(x2-6x+c3)，集合M={x|f（x）=0}={x1，x2，x3，x4，x5}?N*，设c1≥c2≥c3，则c1-c3=（ ） A: 6 B: 8 C: 2 D: 4
- 求函数 f(x)=3*x1^2 + 2*x1*x2 + x2^2 − 4*x1 + 5*x2. 时,输入代码 >>fun = @(x)3*x(1)^2 + 2*x(1)*x(2) + x(2)^2 - 4*x(1) + 5*x(2); >>x0 = [1,1]; >>[x,fval] = fminunc(fun,x0); 到matlab上运行一下,得到的结果,x是: