Matlab结果用小数显示

1、一般情况
format long或format short

format long
a=2*pi

format short
b=2*pi

2、使用了符号计算
用vpa转换为小数显示

clear
clc
syms X1 X2 X3 X4
b=[4,4,4,4;%1
    1,1,1,1;%2
    8,8,8,8;%3
    6,6,6,6;%4
    3,7,3,7;%5
    ];
a=b'
c=[0.1;0.2;0.2;0.4;0.4];
S1=(X1-a(1,1)).^2+(X2-a(2,1)).^2+(X3-a(3,1)).^2+(X4-a(4,1)).^2+c(1);
S2=(X1-a(1,2)).^2+(X2-a(2,2)).^2+(X3-a(3,2)).^2+(X4-a(4,2)).^2+c(2);
S3=(X1-a(1,3)).^2+(X2-a(2,3)).^2+(X3-a(3,3)).^2+(X4-a(4,3)).^2+c(3);
S4=(X1-a(1,4)).^2+(X2-a(2,4)).^2+(X3-a(3,4)).^2+(X4-a(4,4)).^2+c(4);
S5=(X1-a(1,5)).^2+(X2-a(2,5)).^2+(X3-a(3,5)).^2+(X4-a(4,5)).^2+c(5);
f1x=-(1./S1+1./S2+1./S3+1./S4+1./S5);
df1=gradient(f1x);
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%以上只是在定义符号函数和求导，不用管
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f1=vpa(subs(f1x,{X1,X2,X3,X4},{4,4,4,4}))
df1=vpa(subs(df1,{X1,X2,X3,X4},{4,4,4,4}))