Add instructions on input data format

doc/IO_formating.md

@@ -0,0 +1,41 @@
+# AutoEIS Input Data Format Guide
+
+As demonstrated in the [example notebook](https://github.com/AUTODIAL/AutoEIS/blob/main/examples/demos/basic_workflow.ipynb), AutoEIS requires access to two specific features from the measured EIS data:
+- **Impedance Data (Complex Values)**: Denoted as *Z* in the sample file.
+- **Measurement Frequencies**: Denoted as *freq*.
+
+Due to the variety of devices and settings used for EIS analysis, the collected data often comes in different formats, presenting challenges for developing a universal data loading function. To address this, we suggest users customize their data loading process as described below.
+
+## General Formats
+For common EIS data formats, you can load them using the following methods:
+- **CSV (.csv)**: `pandas.read_csv`
+- **JSON (.json)**: `pandas.read_json` or `json.load()`
+- **Spreadsheets (.xls, .xlsx)**: `pandas.read_excel`
+- **Text file (.txt)**: `numpy.loadtxt`
+
+## Device-Specific Formats
+For specific formats provided by measurement devices, consider using additional packages such as [pyimpspec](https://vyrjana.github.io/pyimpspec/index.html):
+- **BioLogic**: (.mpt)
+- **Eco Chemie**: (.dfr)
+- **Gamry**: (.dta)
+- **Ivium**: (.idf) and (.ids)
+
+## The `pyimpspec` Package
+[`pyimpspec`](https://vyrjana.github.io/pyimpspec/index.html) is a Python library designed to handle and process spectroscopic data. It supports loading EIS data from various proprietary formats and converting them into a format compatible with AutoEIS, facilitating easy data access.
+
+## Example Usage
+Below is an example demonstrating how to use `pyimpspec` to load a proprietary EIS data format and access the impedance data.
+
+```python
+# !pip install pyimpspec
+
+from pyimpspec import DataSet, parse_data
+
+# Load EIS data from a proprietary format
+data: DataSet
+for eis_data in parse_data("path/to/your/data.dta"):
+    loaded_eis = eis_data.to_dataframe()
+
+    # Extract frequency and complex impedance data
+    freq = loaded_eis["f (Hz)"].values
+    Z = loaded_eis["Re(Z) (ohm)"].values + loaded_eis["Im(Z) (ohm)"].values * 1j

doc/index.rst

@@ -27,5 +27,6 @@ Contents
 
    installation.md
    basic_usage.md
+   IO_formating.md
    circuit.md
    modules.rst