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https://github.com/mrc-ide/cinterpolate
:bar_chart::arrow_right::wavy_dash: Interpolating functions from C, in R
https://github.com/mrc-ide/cinterpolate
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Last synced: about 2 months ago
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:bar_chart::arrow_right::wavy_dash: Interpolating functions from C, in R
- Host: GitHub
- URL: https://github.com/mrc-ide/cinterpolate
- Owner: mrc-ide
- License: other
- Created: 2017-10-04T09:58:00.000Z (about 7 years ago)
- Default Branch: master
- Last Pushed: 2024-09-17T16:37:08.000Z (4 months ago)
- Last Synced: 2024-09-17T20:48:33.033Z (4 months ago)
- Topics: infrastructure
- Language: C
- Homepage: https://mrc-ide.github.io/cinterpolate
- Size: 521 KB
- Stars: 9
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# cinterpolate
[](https://www.repostatus.org/)
[](https://github.com/mrc-ide/cinterpolate/actions/workflows/R-CMD-check.yaml)
[](https://app.codecov.io/github/mrc-ide/cinterpolate?branch=master)
[](https://cran.r-project.org/package=cinterpolate)
Simple interpolation functions designed to be used from C. There is essentially no R support in this package, save code designed to be used by the package's own testing. `cinterpolate` is designed to be used in package code only and modification for use outside of a package is not explicitly supported.
## Installation
`cinterpolate` is now on CRAN and can be installed with
```r
install.packages("cinterpolate")
```
### Development version
After that, install with
```r
install.packages(
"orderly2",
repos = c("https://mrc-ide.r-universe.dev", "https://cloud.r-project.org"))
```
If you install from source, this package requires a fortran compiler because it uses LAPACK and BLAS, despite being only C code.
* **macOS** Install Xcode, confirm the command line tools are installed and then install gfortran following [these instructions](https://cran.r-project.org/bin/macosx/tools/)
* **windows** [Rtools](https://cran.r-project.org/bin/windows/Rtools/) includes gfortran
* **linux** Something like `apt-get install gfortran` depending on your platform
## Usage
``` c
#include
```
Allocate an object to perform interpolation with. `nx` and `x` are the size and values of the function to be interpolated, while `ny` is the number of functions to be simultaneously (but independently) interpolateed and `y` is the values for these. If `ny > 1`, then the values of `y` are as an R matrix with `nx` rows and `ny` columns (the first `nx` values are the first function, the second `nx` are the second, and so on). The final two are booleans: `fail_on_extrapolate` throws an error if extrapolation is requested, and `auto_free` uses `R_alloc()` rather than `Calloc` allowing automatic cleanup.
``` c
void *obj = cinterpolate_alloc(type, nx, ny, x, y,
fail_on_extrapolate, auto_free);
```
With the interpolation function, an input value of `xout` and given some storage `yout` of length `ny`, determine `f(xout)` with
``` c
cinterpolate_eval(xout, obj, yout);
```
Once done the object must be freed with
```
cinterpolate_free(obj);
```
### Further package setup
Somewhere in the package you must include `cinterpolate.c` as
``` c
#include
```
but this must be included **only once** or linking will fail. If you only use the interpolation in one place, you can use `cinterpolate.c` rather than `cinterpolate.h`. If you use interpolation in more than once place, I recommend a file `src/cinterpolate.c` containing
``` c
#include
```
Be sure to include in your `DESCRIPTION` a line
```
LinkingTo: cinterpolate
```
`cinterpolate` takes advantage of BLAS for matrix multiplication, so you may need a Makevars that includes
```make
PKG_LIBS = ${LAPACK_LIBS} ${BLAS_LIBS} ${FLIBS}
```
### Example
See [`inst/example`](inst/example) for a full example of using `cinterpolate` within a package
## License
MIT + file LICENSE © Imperial College of Science, Technology and Medicine
Please note that this project is released with a [Contributor Code of Conduct](https://mrc-ide.github.io/cinterpolate/CONDUCT).
By participating in this project you agree to abide by its terms.