# How to read Arrow.jl files from R?
**URL:** https://discourse.julialang.org/t/how-to-read-arrow-jl-files-from-r/56178
**Category:** General Usage
**Tags:** data, r, arrow
**Created:** [February 28, 2021, 9:43am UTC](https://discourse.julialang.org/t/how-to-read-arrow-jl-files-from-r/56178 "2021-02-28T09:43:02Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@jzr](https://discourse.julialang.org/u/jzr)
#### Post date: [February 28, 2021, 9:43am UTC](https://discourse.julialang.org/t/how-to-read-arrow-jl-files-from-r/56178/1 "2021-02-28T09:43:02Z")
I used `Arrow.write()` from Arrow.jl 1.2.4 and `read_feather()` from R arrow 3.0.0 but the read said errored:
```julia
Error in ipc ___feather___ Reader__Open(file) :
Invalid: Not a Feather V1 or Arrow IPC file
```
How can I read this file from R?
---
### Author:  [@dmbates](https://discourse.julialang.org/u/dmbates)
#### Post date: [February 28, 2021, 6:54pm UTC](https://discourse.julialang.org/t/how-to-read-arrow-jl-files-from-r/56178/2 "2021-02-28T18:54:43Z")
I don’t have difficulty with that combination on Ubuntu 20.10
```julia
bates$ julia-1.5.3 -t auto -O3
_
_ _ _(_)_ | Documentation: https://docs.julialang.org
(_) | (_) (_) |
_ _ _| |_ __ _ | Type "?" for help, "]?" for Pkg help.
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 1.5.3 (2020-11-09)
_/ |\ __'_|_|_|\__'_| | Official https://julialang.org/ release
|__/ |
julia> using Arrow
(@v1.5) pkg> status Arrow
Status `~/.julia/environments/v1.5/Project.toml`
[69666777] Arrow v1.2.4
julia> Arrow.write("/tmp/arrowtest.arrow", (x = rand(6), f = repeat(["A","B"], inner=3)))
"/tmp/arrowtest.arrow"
julia>
bates$ R
R version 4.0.4 (2021-02-15) -- "Lost Library Book"
Copyright (C) 2021 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)
R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.
Natural language support but running in an English locale
R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.
Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.
> require("arrow")
Loading required package: arrow
Attaching package: ‘arrow’
The following object is masked from ‘package:utils’:
timestamp
> read_feather("/tmp/arrowtest.arrow")
x f
1 0.9617653 A
2 0.4586787 A
3 0.3014748 A
4 0.4049147 B
5 0.6989243 B
6 0.3541891 B
```
---
### Author:  [@jzr](https://discourse.julialang.org/u/jzr)
#### Post date: [February 28, 2021, 10:52pm UTC](https://discourse.julialang.org/t/how-to-read-arrow-jl-files-from-r/56178/3 "2021-02-28T22:52:21Z")
```julia
open("/tmp/my.arrow", "w") do f; RDatasets.dataset("ggplot2", "diamonds")) end
```
works with R’s `read_feather("/tmp/my.arrow")` but
```julia
open("/tmp/my.arrow", "w") do f
Arrow.write(f, RDatasets.dataset("ggplot2", "diamonds"))
end
```
gives an error in R
```julia
> df = read_feather("/tmp/my.arrow")
Error in ipc ___feather___ Reader__Open(file) :
Invalid: Not a Feather V1 or Arrow IPC file
```
---
### Author:  [@dmbates](https://discourse.julialang.org/u/dmbates)
#### Post date: [March 1, 2021, 3:16pm UTC](https://discourse.julialang.org/t/how-to-read-arrow-jl-files-from-r/56178/4 "2021-03-01T15:16:54Z")
I think we may need @quinnj to weigh in here. `Arrow.write` can write either the file format or the memory format and I suspect that is the distinction here. The file format has a magic number in the first 6 characters of “ARROW1”
```julia
julia> String(read("/tmp/my.arrow")[1:6])
"ARROW1"
```
---
### Author:  [@quinnj](https://discourse.julialang.org/u/quinnj)
#### Post date: [March 1, 2021, 5:15pm UTC](https://discourse.julialang.org/t/how-to-read-arrow-jl-files-from-r/56178/5 "2021-03-01T17:15:47Z")
Hmmm, weird. So there are 3 distinct formats possible:
- Feather V1: this is pre-arrow 1.0, which supported only a subset of full arrow type spec and had a few other minor differences
- Arrow IPC: this is the arrow “in memory” format in raw bytes, often used by being sent over the wire via HTTP request or gRPC, or you could just save these bytes to disk
- Arrow file: this is basically the same as “in memory” format written to disk, but includes a little extra metadata to enable “random access” to specific record batches within a file. This is also known as Feather V2
So it seems weird that the R package says it expects a Feather V1 or an Arrow IPC, but seems to not be able to read Feather V2? Or maybe I’m getting this backwards because it seems from your example that if you try to write to a filename as a String (which produces Feather V2) that seems to work, but the IPC doesn’t?
---
### Author:  [@dmbates](https://discourse.julialang.org/u/dmbates)
#### Post date: [March 1, 2021, 5:32pm UTC](https://discourse.julialang.org/t/how-to-read-arrow-jl-files-from-r/56178/6 "2021-03-01T17:32:41Z")
I think it may be the error message from the R arrow package that is incorrect. I certainly have had no problem reading the Feather V2 format files in R.
---
### Author:  [@quinnj](https://discourse.julialang.org/u/quinnj)
#### Post date: [March 1, 2021, 6:01pm UTC](https://discourse.julialang.org/t/how-to-read-arrow-jl-files-from-r/56178/7 "2021-03-01T18:01:36Z")
Yeah, looking back over the examples, I think that’s right. I think they don’t support reading the raw arrow IPC messages.
---
### Author:  [@dmbates](https://discourse.julialang.org/u/dmbates)
#### Post date: [March 2, 2021, 3:19pm UTC](https://discourse.julialang.org/t/how-to-read-arrow-jl-files-from-r/56178/8 "2021-03-02T15:19:45Z")
I think another function, `read_ipc_stream`, is used for reading the raw arrow IPC messages.