Question

如何用mathematica画分段函数图形

我想用mathematica画个分段函数的图形，如0<x<5时为x^2+6,在5<x<8时为-3x,有谁能帮个忙啊，谢谢了

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);

　　

Answer 2

f[x_]:=x^2+6/;0<x<5
f[x_]:=-3x/;5<x<8
Plot[f[x],{x,0,8}]

Answer 3

f[x_]:=Which[0<x&&x<5,x^2+6,5<x&&x<8,-3x]