# Questions about DataFrame
**URL:** https://discourse.julialang.org/t/questions-about-dataframe/89813
**Category:** New to Julia
**Tags:** question, dataframes
**Created:** [November 5, 2022, 2:05pm UTC](https://discourse.julialang.org/t/questions-about-dataframe/89813 "2022-11-05T14:05:22Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@zhangchunyong](https://discourse.julialang.org/u/zhangchunyong)
#### Post date: [November 5, 2022, 2:05pm UTC](https://discourse.julialang.org/t/questions-about-dataframe/89813/1 "2022-11-05T14:05:22Z")
I have a DataFrame like the following.I want to use the each row’s first ,second col and third ,forth col to do t test.
```julia
using DataFrames,HypothesisTests
a=DataFrame(x=[1,2,3,4,5,6,7,8,9,10.2],b=[0.1,0.5,1,2,3,4,3,5,6,7],c=[0.9,0.6,0.7,6,8,4,6,7,3,1],d=[0.2,2,0.3,6,3,5,6,8,7,9])
10×4 DataFrame
Row │ x b c d
│ Float64 Float64 Float64 Float64
─────┼────────────────────────────────────
1 │ 1.0 0.1 0.9 0.2
2 │ 2.0 0.5 0.6 2.0
3 │ 3.0 1.0 0.7 0.3
4 │ 4.0 2.0 6.0 6.0
5 │ 5.0 3.0 8.0 3.0
6 │ 6.0 4.0 4.0 5.0
7 │ 7.0 3.0 6.0 6.0
8 │ 8.0 5.0 7.0 8.0
9 │ 9.0 6.0 3.0 7.0
10 │ 10.2 7.0 1.0 9.0
julia> pvalue(OneSampleTTest([1.0,0.1],[0.9,0.2]))# like the left writings in each row.
0.9999999999999999
```
If I want to do the t test for this dataframe 's 10 rows.Should I do like the following?
```julia
julia> pval=Float64[]
Float64[]
julia> for i in 1:nrow(a)
a1=[a[i,:][1],a[i,:][2]] #if I have 100 columns,it is not a good way
a2=[a[i,:][3],a[i,:][4]]
pv=pvalue(OneSampleTTest(a1,a2))
push!(pval,pv)
end
julia> pval
10-element Vector{Float64}:
0.9999999999999999
0.978056288767978
0.3119165215094772
0.20483276469913345
0.49999999999999944
0.7951672353008665
0.7048327646991336
0.7048327646991336
0.605136913422507
0.6362752636432489
```
I used for loop through each row of the data frame and take the elements in each row to do the t test.Are there any easy ways to do so? Thanks for helping me !
---
### Author:  [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)
#### Post date: [November 5, 2022, 2:31pm UTC](https://discourse.julialang.org/t/questions-about-dataframe/89813/2 "2022-11-05T14:31:12Z")
Maybe the following?
```julia
julia> a=DataFrame(x=[1,2,3,4,5,6,7,8,9,10.2],b=[0.1,0.5,1,2,3,4,3,5,6,7],c=[0.9,0.6,0.7,6,8,4,6,7,3,1],d=[0.2,2,0.3,6,3,5,6,8,7,9]);
julia> a.pvals = map(eachrow(a)) do row
a1 = collect(row[1:2])
a2 = collect(row[3:4])
pvalue(OneSampleTTest(a1, a2))
end
10-element Vector{Float64}:
0.9999999999999999
0.978056288767978
0.3119165215094772
0.20483276469913345
0.49999999999999944
0.7951672353008665
0.7048327646991336
0.7048327646991336
0.605136913422507
0.6362752636432489
julia> df = DataFrame(rand(1000, 100), :auto);
julia> df.pvals = map(eachrow(df)) do row
a1 = collect(row[1:50])
a2 = collect(row[51:100])
pvalue(OneSampleTTest(a1, a2))
end
```
---
### Author:  [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)
#### Post date: [November 5, 2022, 10:52pm UTC](https://discourse.julialang.org/t/questions-about-dataframe/89813/3 "2022-11-05T22:52:00Z")
An alternative:
```julia
@views [pvalue(OneSampleTTest(r[1:2], r[3:4])) for r in eachrow(Matrix(a))]
```