Add reference to original xarray project.

README.md

@@ -1,7 +1,35 @@
 # xarray_on_MATLAB
-N-dimensional labeled array, like xarray implemented in Python
+[![View xarray on File Exchange](https://www.mathworks.com/matlabcentral/images/matlab-file-exchange.svg)](https://jp.mathworks.com/matlabcentral/fileexchange/125995-xarray)
 
-# usage
-See livescript:readme.mlx
+# Introduction
+`xarray` is an N-dimensional labeled array, inspired by [xarray](https://github.com/pydata/xarray) implemented in Python.
+The purpose of this `xarray` on MATLAB project is basically a port of the original (Python) xarray.
 
-[![View xarray on File Exchange](https://www.mathworks.com/matlabcentral/images/matlab-file-exchange.svg)](https://jp.mathworks.com/matlabcentral/fileexchange/125995-xarray)
+# Feature
+Currently, `xarray` has a class of arrays called `DataArray`. Here is an example of the 2x3 2-dimensional `DataArray`
+```
+da = xarray.DataArray([10.1 10.4 12.3; 20.3 20.5 24.2] ...
+, dims = {'x', 'time'}...
+, coords = {'x', [2.5, 4.4], 'time', [0 .1 .2]})
+```
+## Accessing with Label
+The most important feature of `DataArray` is the ability to select array elements by axis name. From the data above, we slice out the array for 
+```
+da.sel(x=4.4)
+```
+This selection method is revolutionary in two ways.
+1. You do not have to remember the dimension number of the axis (in this case, `x` is the first dimension of the data array).
+2. No need to calculate the index on the axis that is desired value (in this case, the second element of the `x` axis).
+
+The second point could be realized by writing `matlab_array(:,x_vec==4.4)` and so on. However, not having to remember the dimension of the axis is useful when dealing with data that has many dimensions.
+## Accessing as MATLAB style
+The element of DataArray can be accessed also by conventional MATLAB array style. This is an example which has same result as written above.
+```
+data(2,:)
+```
+# Detailed Usage
+See comparison_table.md for a table comparing how `xarray` on MATLAB is written with the original `xarray` notation.
+Also, see readme.mlx for tutorial.
+
+# Installation
+Just copy +xarray folder to your folder contained the code.

comparison_tables.md

@@ -0,0 +1,18 @@
+# Reference for xarray
+
+## Comparison table
+|function|xarray on python|xarray on MATLAB<br>(This package)|
+| ---- | ---- | ---- |
+| Create|DataArray(data) |DataArray(data)  |
+|Lookup| (see below)|(see below)|
+|Sum| x.sum('time') | x.sum('time') *|
+
+
+
+## Lookup in DataArray
+|Dimension lookup|Index lookup|python|MATLAB|
+|----|----|----|----|
+|Positional|By integer|da[:,0]|da(:,0)|
+|Positional|By label|da[:,'IA']||
+|By name|By integer|da.isel(space=0)<br>da[dict(space=0)]|da(space=1) *|
+|By name|By label|da.sel(space='IA')<br>da.loc[dict(space='IA')]|da.sel(space='IA')<br>da.sel('space', 'IA')|