将数字转换为科学格式的字符串

Question

I have some numbers, such as num = c(0.1, 0.001, 1.12345e-5) . I want to turn num as string, with each element displayed in scientific format, with 3 digits. That is num_after_convert = c( '1.00e-1', '1.00e-3' , '1.12e-5') . Any good solution?

Answer 1

The sprintf function will give you the most control of the output and can guarantee scientific notation:

> num <- c(0.1, 0.001, 1.12345e-5)
> sprintf("%4.2e", num)
[1] "1.00e-01" "1.00e-03" "1.12e-05"
> 

Answer 2

如果你的矢量总是至少有一个元素已经用科学记数法，请尝试这个，如你的例子：

format(num,digits=3)