matlab如何控制数值精度

% vpa函数，控制数值精度，a=3.14159......，取vpa(a,5)后，输出为3.1416

a=pi;

vpa(a,5);

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% round函数，将数据进行四舍五入

round(pi)    %输出为3

round(-1.9) %输出为-2

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