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版本号 V1.4.2（2020-05-23）
一、数学函数
1.round()
四舍五入函数，保留到整数位
julia> round(456.321)
456.0
julia> round(456.521)
457.0
高版本报错，低版本能实现的功能如下：
julia> round(123.54)
124.0
julia> round(123.54,1)
123.5
julia> round(123.54,-1)
120.0
2.rand()和randn()
rand():结果服从[0,1]的均匀分布；
randn()：结果服从N(0,1)的正态分布。
julia> show(rand(9))
[0.9481507680803489, 0.4945941107267209, 0.024940697154182567, 0.5704158279340583, 0.6270574650692144, 0.5003381646018885, 0.26248735776413357, 0.26685131628428826, 0.12640432182698547]
得到一个3*2的数据集
julia> show(rand(3,2))
[0.9186417696309077 0.3274585091521769;
0.3649384914441276 0.6292180877607207;
0.909662033678333 0.6009276756647459]
julia> show(rand(Int8,10))
Int8[71, 2, 79, 101, -46, -67, 29, 26, -44, -53]
julia> show(rand(Bool,10))
Bool[1, 0, 0, 1, 0, 1, 1, 1, 1, 0]
给定数据区间的整数组
julia> show(rand(1:6,10))
[6, 1, 6, 6, 5, 1, 3, 5, 5, 6]
julia> show(randn(10))
[2.4737348494389457, 0.02381500170203782, -0.06133256088133444, -0.6994129834660351, -0.605475467534163, 0.9128761414810291, -1.2132405170942984, -0.09117753461036124, 0.3269714960309829, -0.9200957668459002]
srand表示随机数，但是只在低版本支持
julia> srand(12345)
julia> show(randn(6))
[1.1723579360368195,0.8527074591390049,0.4155652148758223,0.5164248452392485,
0.6857588179209828,0.28227210708857803]
3.sum()
julia> A = Array(Int64,3,4);A[:] = 1:12;show(A)
3x4 Array{Int64,2}:
1 4 7 10
julia>
2 5 8 11
3 6 9 12
对列求和
julia> sum(A,1)
1x4 Array{Int64,2}:
6 15 24 33
对行求和
julia> sum(A,2)
3x1 Array{Int64,2}:
22
26
30
对布尔值求和
julia> sum([true,false,true,true,false])
3
4.mean()函数
julia> mean([1,2,3])
2.0
julia> mean([true,false])
0.5
julia> mean(A,1)
1x4 Array{Float64,2}:
2.0 5.0 8.0 11.0
julia> mean(A,2)
3x1 Array{Float64,2}:
5.5
6.5
7.5