首先,建立自定义分段函数,即piecewise。m function y=piecewise(x) %piecewise function 分段函数 n=length(x); Pomax=9; for i=1:n if x(i)>=0 & x(i)<=150 y(i)=0.79*Pomax*x(i)^0.048; elseif x(i)>150 & x(i)<=270 y(i)=Pomax*exp(-0.021*(x(i)-150)); else disp('x必须在0~270之间') end end 然后,在当前目录下,执行 >> piecewise(4) ans = 7.5992