added part about statistics, small fixes

1 files changed, 36 insertions, 4 deletions

diff --git a/matlab_usage_source/index.t2t b/matlab_usage_source/index.t2t
index a8c14d4..d09131e 100644
--- a/matlab_usage_source/index.t2t
+++ b/matlab_usage_source/index.t2t
@@ -13,7 +13,7 @@ you need  to process multiple  data point it  became tedious with  a simple
 calculator. Once  you master Matlab  it will not matter  if it is  one data
 point or millions of them. It  can do complex math, plotting, fitting, etc.
 It is also the complete programming language which can stand by itself.
-Also, Matlab has excellent help documentation and a lot of tutorials at the web.
+Also, Matlab has **excellent help documentation** and a lot of tutorials at the web.
 
 There are free alternatives. [Octave  http://www.gnu.org/software/octave/]
 is  one example. This what I personally use
@@ -30,10 +30,42 @@ Since we are learning Matlab, we will not  have time to go to fancy toolboxes
 which Matlab provides/removes with new releases. 
 
 
+= Statistics functions =
+
+== Mean of a set ==
+Often you will need to find the mean and standard deviation of a particular
+sample set. Let's say we estimated  a resistor value (**R**) with different
+method and obtained the following experimental values.
+
+| **R**  | 1.20 | 1.10 | 1.11 | 1.05 | 1.05 | 1.15 |
+
+First we transfer it to a Matlab vector variable
+``` R=[ 1.20, 1.10, 1.11, 1.05, 1.05, 1.15 ]
+
+Notice that for a vector variable I use **,** as a separator.
+
+Now we ready to calculate mean of this set
+``` mean(R)
+with answer 1.1100
+
+== Standard deviation of a set ==
+Standard deviation normalized with **N-1** samples  (so called unbiased estimator)
+is done with
+``` std(R)
+with answer 0.058310. If you need normalization with **N** samples do
+``` std(R,1)
+with answer 0.053229
+
+In both  cases there is  to many  significant figures which  is unjustified
+from physics point of view. So remember, Matlab just does the math for you,
+the analysis and presentation of results is on you.
+
+
+
 = How to make a simple plot =
 Suppose during the measurements we obtain the following data
-for each current value 'I' we measured voltage 'V' 
-with some uncertainty in voltage measurement dV.
+for each current value **I** we measured voltage **V**
+with some uncertainty in voltage measurement **dV**.
 Our experimental data is represented in the following table.
 
 || I   | V   | dV  |
@@ -43,7 +75,7 @@ Our experimental data is represented in the following table.
 |  3.3 | 3.8 | 0.2 |
 |  4.0 | 4.9 | 0.3 |
 
-First of all,  we need to transfer  it to the Matlab  vector variables. Pay
+First of all,  we need to transfer  it to the Matlab column vector variables. Pay
 attention to the delimiter **;** between numbers
 
 ```