of a letter means the cumulative confidence of the letter to the right sets letter. Similarly right support and confidence carry the meaning as well.

## 4. Proposed Algorithm

1. Find out the most frequent item set of monograph (letter) in descending order 2. Distribute 1st and 4th letter in the right hand (as 1 st letter found twice of second)
3. Distribute 2nd and 3rd letter in the left hand 4. Now take the letter one by one starting from 5th letter and distribute it in left hand or right depend on the following criteria a. Find the cumulative support and confidence of this character with all right hand letter distributed till now and labeled it as right support and right confidence b. Similarly find left support and left confidence for the same letter c. if left support > right support and left confidence > right confidence then distribute the letter in right side otherwise in left side.

 5. Repeat the step 4 until all letters are distributed.

## 5. Experimental **Result**

About more than 8 lakh letters are extracted from various types of documents such as prose, text book, novel, religious book etc. From this data we find out monographs, digraphs and then determine support and confidence to mine the association.

Table 1: The first ten monograms of our experiment

Letter Frequency Percentage

74300 9.039875 45525 5.538901

41844 5.091044 37010 4.502904 31214 3.797721 28996 3.527863 28212 3.432476 21451 2.609884 18419 2.240989

17202 2.092920

So according to the 1-3 steps of the algorithm we can 

initialize the left and right side characters, which are as 

follows: Right { }, left { } Now we have to take 

the decision in which set the 5th character will lies. The 

decision is depend on the step 4.

Table 2: The association of ka( ) with some letters are 

as follows

Digraph Frequency Support Confidence

8316 1.011785 21.717897

 8000 0.973338 20.892638 4134 0.502972 10.796271 3094 0.376438 8.080228

2062 0.250878 5.385077

1231 0.149772 3.214855 1153 0.140282 3.011151

The support and confidence of K with left item set 

{ } is 

  1.011785 21.717897

 0.502972 10.796271

(After addition) 1.514757 32.514168

So left support (cumulative) is 1.5154757 

left confidence (cumulative) is 32.514168 The support and confidence of K with right item set { } is

0.973338 20.892638

0.376438 8.080228

(After addition)

1.349776 28.972866

So right support (cumulative) is 1.349776 Right confidence is 28.972866. In this example left support is greater then right support and left confidence is greater right confidence. Thus will go to right item sets. As a result the members of item sets are increased. The sets Right { } and left { } Thus all letter are distribute in left and right side according to the descending order of the frequency of the letter. After executing the program we got the following two sets Right{
 } Left 
{ } Then we distribute the letter according to the most frequent occurring letter in middle row that is closer to the hand as described in the algorithm at step 4. Our designed Bangla keyboard layout is below.

$${\bf\nabla}\cdot\hat{\Gamma}\uparrow\overline{{{\Phi}}}$$
$$\overleftarrow{\flat}\rtimes\rtimes\boxtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes\rtimes$$ with shift key
$$\frac{\mathrm{Confidence}}{21.717897}$$
