Usage¶

Pattern selection¶

Select the second scan or a measured CIF block:

import geddes

pattern = geddes.read("measurement.rasx", index=1)
pattern = geddes.read("standard.cif", block="_meas")

fn main() -> Result<(), geddes::Error> {
    let options = geddes::ReadOptions { index: 1, block: None };
    let pattern = geddes::read_with_options("measurement.rasx", &options)?;

    let options = geddes::ReadOptions {
        block: Some("_meas".into()), ..Default::default()
    };
    let pattern = geddes::read_with_options("standard.cif", &options)?;
    Ok(())
}

const geddes = require('@jcwang587/geddes')

const pattern = geddes.read('measurement.rasx', { index: 1 })
const measured = geddes.read('standard.cif', { block: '_meas' })

Indices follow file order. An out-of-range index or unmatched block raises an error. CIF and single-pattern formats require index=0; a CIF substring selects the first matching profile block.

Reading bytes¶

Pass the file contents and a filename hint. The filename does not open a file.

import geddes

pattern = geddes.read_bytes(b"10 4\n11 9\n12 16\n", "sample.xy")

fn main() -> Result<(), geddes::Error> {
    let pattern = geddes::read_bytes(b"10 4\n11 9\n12 16\n", "sample.xy")?;
    Ok(())
}

const geddes = require('@jcwang587/geddes')

const data = Buffer.from('10 4\n11 9\n12 16\n')
const pattern = geddes.readBytes(data, 'sample.xy')

Byte readers accept the same selection options. Rust also supports Read + Seek streams through from_reader; see Rust in the API reference.

Intensity values¶

Intensities retain their stored units. Counts per second are not converted to counts.

Geddes returns x/y only. It does not smooth, resample, subtract backgrounds, calculate uncertainties, or remove points with zero uncertainty or weight.

Ordering and validation¶

• Arrays: Finite, nonempty, and equally sized.
• Strictly descending scans: Reversed as paired x/y arrays.
• Invalid axes: Duplicate positions or changes in direction raise errors.
• Constructors: Direct Pattern constructors require increasing x.

Geddes does not convert Q, d-spacing, or time-of-flight axes. See Limits in Supported formats for inputs without a reliable axis declaration.

Using the arrays¶

These Python examples use the toy pattern. Install Matplotlib and NumPy for plotting and CSV export:

pip install matplotlib numpy

Plot x and y:

import geddes
import matplotlib.pyplot as plt

pattern = geddes.read("profile.xy")
plt.plot(pattern.x, pattern.y, "o-")
plt.xlabel("2θ (degrees)")
plt.ylabel("Intensity")
plt.show()

Save a two-column CSV:

import geddes
import numpy as np

pattern = geddes.read("profile.xy")
xy = np.column_stack((pattern.x, pattern.y))
np.savetxt("profile.csv", xy, delimiter=",", header="2theta,intensity", comments="")