# Comodo Calculator

**Version:** 3.2.3 (Mercurial revision 5770:c90c3015e72d, 2026-05-22)

---

## Description

`comodo-calculator` is a **calculator, variable extractor, and compiler** for scientific data. It supports input files in **NetCDF, GRIB, GeoTIFF, and ASCII** formats. The output format defaults to NetCDF but can be **GeoTIFF** if the last input file is in GeoTIFF format.

For ASCII inputs, specify column indices as variable names (e.g., `time=col0`).

---

## Usage

```bash
comodo-calculator -i file1.nc [var1]=ncVarName1 [ncPhaseVarName1] [[AXES:n0,...]] [ [var2]=ncVarName2 ...] [-i file2.nc ...] [OPTIONS]
```

---

## Options


| Option             | Description                                                                                                   |
| ------------------ | ------------------------------------------------------------------------------------------------------------- |
| `-h, --help`       | Display help and exit.                                                                                        |
| `-i <file>`        | Path to an input file (NetCDF, GRIB, GeoTIFF, or ASCII).                                                      |
| `-o <file>`        | Path to the output file.                                                                                      |
| `-f <formula>`     | Formula to apply. If it starts with `/`, `./`, or `../`, it is treated as a file path containing the formula. See below for valid [function and variables](#function). |
| `-deflate <level>` | Compression level for NetCDF output. Default is `4`.                                                          |
| `--create=no`      | Preserve the input file if it is identical to the output file.                                                |
| `--fixed-types`    | Enforce fixed data types.                                                                                     |


---

## Examples

### Extract Variables from a File

```bash
comodo-calculator -i grid.nc =longitude =latitude =depth -o bathymetry.nc
```

### Add Variables to an Existing File

```bash
comodo-calculator -i tugo.state-2018.01.nc =time =bathymetry =lon =lat =triangles =edges =elevation =ubar =vbar -o tugo.state-2018.01-reduced.nc
```

### Extract Variables from Multiple Files into One

```bash
comodo-calculator -i grid.nc =longitude =latitude =depth -i modelOutput.nc =elevation -o extract.nc
```

### Extract and Rename Variables from Multiple Files

```bash
comodo-calculator -i grid.nc =longitude =latitude depth1=depth -i modelOutput.nc depth2=depth -o compilation.nc
```

### Compute a Water Index

```bash
comodo-calculator -i T30TXR_20181021T110101_B03_ROI.tiff c=1 -i T30TXR_20181021T110101_B11_ROI.tiff b=1 -f "a=c-b; d=b+c; c=a/d" -o MNDWI.tif
```

### Produce NetCDF from ASCII

```bash
comodo-calculator -i test.dat time=col0 lat=col14 lon=col15 -f "time?atted({units},{days since 1950-01-01})" -o test.nc
```

---

## Notes

- If the output file path ends with `.nc`, it is treated as a NetCDF file.
- If the last input file is a GeoTIFF, the output can also be saved as GeoTIFF.
- Use `--create=no` to avoid overwriting existing files if the input and output are identical.

---

(function)=
## Valid operators, variables and function for formula

### Operators 
 | Name | Description |
 |------|-------------|
 | `+`, `-`, `*`, `/`, `^`, `%` | Addition, difference, product, ratio, power, scalar product |
 
### Variables 

 | Name | Description |
 |------|-------------|
 | `d2r` | Degree to radian (π/180) |
 | `r2d` | Radian to degree (180/π) |
 | `pi` | π |
 | `e` | Exponential |
 | `nan` | Not a number |
 
### Functions 

 | Name | Description |
 |------|-------------|
 | `abs()` | Norm (real or complex) |
 | `arg()` | Phase lag (complex) |
 | `exp()` | Exponential |
 | `gradx()` | Zonal point to point difference |
 | `grady()` | Meridian point to point difference |
 | `cos()` | Cosine |
 | `sin()` | Sine |
 | `sinh()` | Hyperbolic sine |
 | `dx()` | Zonal difference to the neighbor pixel |
 | `dy()` | Meridian difference to the neighbor pixel |
 | `fliph()` | Flip along x-axis |
 | `flipv()` | Flip along y-axis |
 | `nearest()` | Interpolate the masked value with the nearest one |
 | `ellipseM(X,Y)` | Norm of vector or maximum current of ellipse |

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## See Also

- [NetCDF Documentation](https://www.unidata.ucar.edu/software/netcdf/)
- [GDAL Documentation](https://gdal.org/) (for GeoTIFF support)