lejon

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Archive for April, 2014

Index a DataFrame subset on string column name in Julia

Apr 12

Posted by lejon in Computing, julia | Comments off


julia> using RDatasets

julia> iris = dataset("datasets", "iris")

julia> iris[iris[:Species] .== "setosa", :]
50x5 DataFrame
|-------|-------------|------------|-------------|------------|----------|
| Row # | SepalLength | SepalWidth | PetalLength | PetalWidth | Species |
| 1 | 5.1 | 3.5 | 1.4 | 0.2 | "setosa" |
| 2 | 4.9 | 3.0 | 1.4 | 0.2 | "setosa" |
| 3 | 4.7 | 3.2 | 1.3 | 0.2 | "setosa" |
| 4 | 4.6 | 3.1 | 1.5 | 0.2 | "setosa" |
| 5 | 5.0 | 3.6 | 1.4 | 0.2 | "setosa" |
| 6 | 5.4 | 3.9 | 1.7 | 0.4 | "setosa" |
| 7 | 4.6 | 3.4 | 1.4 | 0.3 | "setosa" |
| 8 | 5.0 | 3.4 | 1.5 | 0.2 | "setosa" |
| 9 | 4.4 | 2.9 | 1.4 | 0.2 | "setosa" |

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Nice post on Julia meta operations

Apr 8

Posted by lejon in Computing, julia | Comments off

Great post about basic Julia stuff @ Julia Helps

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Sample with replacement from DataFrame in Julia

Apr 8

Posted by lejon in julia | Comments off

julia> df = DataFrame(A = 1:10, B = 2:2:20)

10x2 DataFrame
|-------|----|----|
| Row # | A | B |
| 1 | 1 | 2 |
| 2 | 2 | 4 |
| 3 | 3 | 6 |
| 4 | 4 | 8 |
| 5 | 5 | 10 |
| 6 | 6 | 12 |
| 7 | 7 | 14 |
| 8 | 8 | 16 |
| 9 | 9 | 18 |
| 10 | 10 | 20 |

julia> df[sample([1:size(df,1)],20),:]

20x2 DataFrame
|-------|----|----|
| Row # | A | B |
| 1 | 2 | 4 |
| 2 | 3 | 6 |
| 3 | 1 | 2 |
| 4 | 4 | 8 |
| 5 | 3 | 6 |
| 6 | 5 | 10 |
| 7 | 8 | 16 |
| 8 | 5 | 10 |
| 9 | 4 | 8 |
| 10 | 8 | 16 |
| 11 | 9 | 18 |
| 12 | 10 | 20 |
| 13 | 9 | 18 |
| 14 | 4 | 8 |
| 15 | 1 | 2 |
| 16 | 1 | 2 |
| 17 | 3 | 6 |
| 18 | 4 | 8 |
| 19 | 10 | 20 |
| 20 | 7 | 14 |

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Convert a matrix (Array) of Any to a matrix (Array) of floats in Julia

Apr 8

Posted by lejon in Computing, julia | Comments off


convert(Array{Float64},array_of_Anys)

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Sample with replacement from Matrix in Julia

Apr 8

Posted by lejon in julia | Comments off

julia> sample([1 2 3;4 5 6;7 8 9], 10)
10-element Array{Int64,1}:
1
3
7
3
8
6
3
7
5
4

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Sample with replacement from a vector in Julia

Apr 8

Posted by lejon in julia | Comments off

julia> sample([1 2 3], 10)
10-element Array{Int64,1}:
2
3
2
3
1
1
2
1
1
1

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Print array in Julia with four number of decimals

Apr 5

Posted by lejon in Computing | Comments off

The general to limit the number of decimals is:

println((round(Array,number of decimals))

so to get four decimals:

println((round(Array,4))

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