从Matlab图形文件中提取数据

I have a Matlab figure file, "file.fig", and I want to abstract the original data from it. The
following procedures should be processed:

1. open('file.fig'); % open figure file
2. fig_handle = findall(gca, 'type', 'line'); % get figure handle
3. x = get(fig_handle, 'xdata'); % get data of X-axis
4. y = get(fig_handle, 'ydata'); % get data of Y-axis