Question

mathematica中分段函数怎么定义？

如题:比如怎么定义这样一个函数：g[x]=x,0<=x<=1,g[x]=-x,-1<=x<=0

Answer 1

可以直接用If定义函数。也可以用 条件符号"/;"定义成分段的。

比如:

ClearAll;

f := 3 /; x <= 0;

f := 4 /; 0 <= x <= 1;

f := 5 /; 1 <= x <= 2;

f := 6 /; 2 <= x <= 3;

f := 7 /; 3 <= x <= 4;

f := 8 /; 4 <= x

h = Plot, {x, -2, 6}, PlotStyle -> Red, AxesOrigin -> {-2, 2}];

r = First /@ Differences /@ (PlotRange /. Options);

结果图像：

Answer 2

有两种方式
1.这样写 g[x_]:=x/;0<=x<=1
g[x_]:=-x/;-1<=x<=0
2. g[x_]=If[0<=x<=1,0,If[-1<=x<=0],-x]

Answer 3

有两种方式
1.这样写
g[x_]:=x/;0<=x<=1
g[x_]:=-x/;-1<=x<=0
2.
g[x_]=If[0<=x<=1,0,If[-1<=x<=0],-x]