Update documentation

README.md

@@ -1,2 +1,103 @@
 # lowcharts
-Tool to draw low-resolution graphs in terminal
+Tool to draw low-resolution graphs in terminal.
+
+**lowcharts** is meant to be used in those scenarios where we have numerical
+data in text files that we want to display in the terminal to do a basic
+analysis.
+
+An example would be the logs of a service (webserver, database, proxy, container
+orchestration, etc.) where times (or sizes) of requests are logged.  In an ideal
+world you would have those logs accessible via a kibana (or similar) or those
+metrics exposed to a prometheus (or similar) and graphed in a grafana dashboard
+(or similar).  But sometimes we need to cope with non ideal worlds, and
+troubleshoot a service with nothing more of what we can muster in a shell
+terminal.
+
+[![Rust](https://github.com/juan-leon/lowcharts/actions/workflows/test.yml/badge.svg)](https://github.com/juan-leon/lowcharts/actions/workflows/test.yml)
+
+### Usage
+
+Type `lowcharts --help`, or `lowcharts PLOT-TYPE --help` for a complete list of
+options.
+
+[![Sample histogram with lowcharts](resources/histogram-example.png)](resources/histogram-example.png)
+
+Currently two basic types of plots are supported:
+
+#### Histogram
+
+This chart is generated using `python3 -c 'import random; [print(random.normalvariate(5, 5)) for _ in range(100000)]' | lowcharts hist`:
+
+
+
+This was inspired by [data-hacks](https://github.com/bitly/data_hacks).
+However, for some big log files I found that project was slower of what I would
+like, and I found that a rust-compiled binary was better suited to my needs.
+
+
+Options for specifying ranges, chart sizes and input files are supported:
+
+```
+lowcharts hist --max 0.5 --intervals 10 --width 50 data.txt
+Samples = 50090; Min = 0.000; Max = 0.499
+Average = 0.181; Variance = 0.023; STD = 0.154
+each ∎ represents a count of 484
+[0.000 .. 0.050] [14545] ∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
+[0.050 .. 0.100] [ 6111] ∎∎∎∎∎∎∎∎∎∎∎∎
+[0.100 .. 0.150] [ 4911] ∎∎∎∎∎∎∎∎∎∎
+[0.150 .. 0.200] [ 4003] ∎∎∎∎∎∎∎∎
+[0.200 .. 0.250] [ 3745] ∎∎∎∎∎∎∎
+[0.250 .. 0.300] [ 3526] ∎∎∎∎∎∎∎
+[0.300 .. 0.350] [ 3424] ∎∎∎∎∎∎∎
+[0.350 .. 0.400] [ 3332] ∎∎∎∎∎∎
+[0.400 .. 0.450] [ 3215] ∎∎∎∎∎∎
+[0.450 .. 0.500] [ 3278] ∎∎∎∎∎∎
+```
+
+Above examples assume input files with a number per line.  Options for figuring
+out where to look in the input file for values are supported by `regex` option.
+This example logs the time spent by nginx for all of 200K http responses ()
+
+
+```
+$ cat nginx*.log | lowcharts hist --regex ' 200 \d+ ([0-9.]+)' --intervals 10
+Samples = 25080; Min = 0.004; Max = 0.049
+Average = 0.008; Variance = 0.000; STD = 0.006
+each ∎ represents a count of 228
+[0.004 .. 0.009] [20569] ∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
+[0.009 .. 0.013] [ 1329] ∎∎∎∎∎
+[0.013 .. 0.018] [  807] ∎∎∎
+[0.018 .. 0.022] [ 1412] ∎∎∎∎∎∎
+[0.022 .. 0.027] [  363] ∎
+[0.027 .. 0.031] [   27]
+[0.031 .. 0.036] [  128]
+[0.036 .. 0.040] [   22]
+[0.040 .. 0.044] [  240] ∎
+[0.044 .. 0.049] [  183]
+```
+
+#### X-Y Plot
+
+This chart is generated using  `cat ram-usage | lowcharts plot --height 20 --width 50`:
+
+[![Sample plot with lowcharts](resources/plot-example.png)](resources/plot-example.png)
+
+Note that x axis is not labelled.  The tool splits the input data by chunks of a
+fixed size and then the chart display the averages of those chunks.  In other
+words: grouping data by time is not (yet?) supported; you can see the evolution
+of a metric over time, but not the speed of that evolution.
+
+There is regex support for this type of plots.
+
+
+### Building
+
+```
+$ git clone https://github.com/juan-leon/lowcharts
+$ cd lowcharts
+$ cargo install --path .
+```
+
+### Contributing
+
+Feedback, ideas and pull requests are welcomed.

src/app.rs

@@ -1,6 +1,5 @@
 use clap::{self, App, Arg, AppSettings};
 
-// fn add_common_options<'a> (app: App<'a>) -> App<'a> {
 fn add_common_options (app: App) -> App {
 
     const LONG_RE_ABOUT: &str = "\