Skip to content
Merged
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion Project.toml
Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
name = "OffsetArrays"
uuid = "6fe1bfb0-de20-5000-8ca7-80f57d26f881"
version = "0.11.4"
version = "1.0.0"

[compat]
julia = "0.7, 1"
Expand Down
56 changes: 53 additions & 3 deletions README.md
Original file line number Diff line number Diff line change
@@ -1,10 +1,55 @@
# OffsetArrays.jl

[![Build Status](https://travis-ci.org/JuliaArrays/OffsetArrays.jl.svg?branch=master)](https://travis-ci.org/JuliaArrays/OffsetArrays.jl)
[![codecov.io](http://codecov.io/github/JuliaArrays/OffsetArrays.jl/coverage.svg?branch=master)](http://codecov.io/github/JuliaArrays/OffsetArrays.jl?branch=master)
[![PkgEval][pkgeval-img]][pkgeval-url]


OffsetArrays provides Julia users with arrays that have arbitrary
indices, similar to those found in some other programming languages
like Fortran.

## Usage

You can construct such arrays as follows:

```julia
OA = OffsetArray(A, axis1, axis2, ...)
```

where you want `OA` to have axes `(axis1, axis2, ...)` and be indexed by values that
fall within these axis ranges. Example:

```julia
using OffsetArrays
A = reshape(1:15, 3, 5)
println("here is A:")
display(A)
OA = OffsetArray(A, -1:1, 0:4) # OA will have axes (-1:1, 0:4)
println("here is OA:")
display(OA)
@show OA[-1,0] OA[1,4]
```

which prints out

```
here is A:
3×5 reshape(::UnitRange{Int64}, 3, 5) with eltype Int64:
1 4 7 10 13
2 5 8 11 14
3 6 9 12 15
here is OA:
OffsetArray(reshape(::UnitRange{Int64}, 3, 5), -1:1, 0:4) with eltype Int64 with indices -1:1×0:4:
1 4 7 10 13
2 5 8 11 14
3 6 9 12 15
OA[-1, 0] = 1
OA[1, 4] = 15
```

OffsetArrays works for arbitrary dimensionality:

```julia
julia> using OffsetArrays

Expand All @@ -21,7 +66,8 @@ julia> y[-1,-7,-128,-5,-1,-3,-2,-1] += 5
```

## Example: Relativistic Notation
Suppose we have a position vector `r = [:x, :y, :z]` which is naturally one-based, ie. `r[1] == :x`, `r[2] == :y`, `r[3] == :z` and we also want to construct a relativistic position vector which includes time as the 0th component. This can be done with OffsetArrays like
Suppose we have a position vector `r = [:x, :y, :z]` which is naturally one-based, ie. `r[1] == :x`, `r[2] == :y`, `r[3] == :z` and we also want to construct a relativistic position vector which includes time as the 0th component. This can be done with OffsetArrays like

```julia
julia> using OffsetArrays

Expand Down Expand Up @@ -49,7 +95,7 @@ Suppose one wants to represent the Laurent polynomial
```
6/x + 5 - 2*x + 3*x^2 + x^3
```
in julia. The coefficients of this polynomial are a naturally `-1` based list, since the `n`th element of the list
in julia. The coefficients of this polynomial are a naturally `-1` based list, since the `n`th element of the list
(counting from `-1`) `6, 5, -2, 3, 1` is the coefficient corresponding to the `n`th power of `x`. This Laurent polynomial can be evaluated at say `x = 2` as follows.
```julia
julia> using OffsetArrays
Expand All @@ -72,4 +118,8 @@ Notice our use of the `eachindex` function which does not assume that the given

## Notes on supporting OffsetArrays

Julia supports generic programming with arrays that doesn't require you to assume that indices start with 1, see the [documentation](http://docs.julialang.org/en/latest/devdocs/offset-arrays/).
There are several "tricks" that make it easier to support arrays with general indexes, see the [documentation](http://docs.julialang.org/en/latest/devdocs/offset-arrays/).


[pkgeval-img]: https://juliaci.github.io/NanosoldierReports/pkgeval_badges/O/OffsetArrays.svg
[pkgeval-url]: https://juliaci.github.io/NanosoldierReports/pkgeval_badges/report.html
Loading