Update README.md

Author: KoheiYatabe

README.md

@@ -1,2 +1,55 @@
-# DGTtool
-A simple and user-friendly tool for computing STFT/DGT
+# DGTtool for computing STFT/DGT
+A simple and user-friendly MATLAB tool for computing the **short-time Fourier transform (STFT)** and the **discrete Gabor transform (DGT)**. It is designed to be **easy and fast** for practical use.
+
+The following features of DGTtool might be different from the other tools:
+ 1. Parameters are stored inside DGTtool object for user-friendliness.
+ 2. All pre-computation runs only once so that repeated computation of DGT/STFT is fast.
+ 3. Many computations run in parallel for all channels (for multi-channel signal).
+ 4. Perfect reconstruction is very easily realized.
+ 5. Number of frequency bins can be smaller than the window length.
+ 6. Dual and tight windows can be computed easily.
+ 7. Sparse time-frequency representation (reassigned spectrogram) is implemented.
+ 8. Phase visualization tool (plotPhase) is implemented.
+ 9. STFT/DGT can be written in an operator form.
+
+
+# How to Use
+Download **DGTtool.m** and place it in the **Current Folder**.
+
+## 1. Create DGTtool object
+Create a DGTtool object `F` by specifying its parameters.
+```
+F = DGTtool('windowShift',500,'windowLength',1500,'FFTnum',2000,'windowName','Blackman')
+```
+(Note: This step can be done without parameters: `F = DGTtool`. Unspecified parameters are set to default values.)
+
+## 2. Compute spectrogram
+Compute a spectrogram `X` from a signal `x`.
+```
+X = F(x);
+```
+
+## 3. Convert spectrogram back to signal
+Compute the signal `x` from its spectrogram `X`.
+```
+x = F.pinv(X);
+```
+
+## 4. Visualize spectrogram
+Three visualization functions are implemented. A spectrogram is computed and plotted from a time-domain signal `x` (and sampling frequency `fs`, optional).
+```
+F.plot(x,fs)
+F.plotPhase(x,fs)
+F.plotReassign(x,fs)
+```
+
+# Documentation
+To check all functions in DGTtool, please read and run **demo.m**.
+```
+help DGTtool
+```
+and
+```
+doc DGTtool
+```
+provide detailed usage.