Finding equal values, between values, greater than and lesser than values of a matrix based on some values

Hi. Suppose I have matrix A of size (m*n) e.g.

 A = [12  44
      93  43
      128 44
      145 41
      180 41
      220 40
      280 40];

and the a,b,c and d values e.g.

 a = 10
 b = 95
 c = 145
 d = 290

As you know

 a < A(1,1)
 A(2,1) < b < A(3,1)
 c = A(4,1)
 d > A(7,1)

I want Matlab to do above process and search the a,b,c and d values in the A(:,1) and tell me that the a,b,c and d values are lesser than or greater than or equal or lying between what members of A(:,1).

Thanks for your help.

[James Tursa]

For your example, what is the specific output you would want? I.e., do you want the indexes of the values where each of a, b, c, d fit? Or ...? Please provide the exact variable(s) you would like as output for your example.

[mr mo]

I want to know the values a,b,c,d is lying between what members of A(:,1)? or in case of equality I want to know these values a,b,c,d are equal to what members of A(:,1)? and I want to know a,b,c or d is lesser than A(first,1) or not ? and I want to know a,b,c or d is greater than A(end,1) or not ?

[James Tursa]

You did not answer my request. Please provide the exact variable outputs you would like based on your example. I.e., at the end of your code, what variables would you like as output and what specific values would they contain for your example above?

[mr mo]

for this example I want to reach these outputs if we consider that the a,b,c,d values are given to the code respectively, so I want these out puts respectively:

 0 12
 93 128
 145
 280 1000

which means a is lesser than 12 and b is between 93 and 128 and c is equal to 145 and d is between 280 and 1000.

Answer 1

[Andrei Bobrov]

A = [12  44
93  43
128 44
145 41
180 41
220 40
280 40];
a = 10;
b = 95;
c = 145;
d = 290;

ii_interval_of_1st_column_of_A = discretize([a,b,c,d],[-inf;A(:,1);inf]);

[mr mo]

Thanks for your help. I think this process may be confused me if I have some large numbers of a,b,c,d or the size of matrix A is large. All I need is I want to know the values a,b,c,d is lying between what members of A(:,1)? or in case of equality I want to know these values a,b,c,d are equal to what members of A(:,1)? and I want to know a,b,c or d is lesser than A(first,1) or not ? and I want to know a,b,c or d is greater than A(end,1) or not ?

[Andrei Bobrov]

AA = [-inf;A(:,1);inf];
Aout = hankel(AA(1:end-1),AA(end-1:end));
ii = discretize([a,b,c,d],AA);
out = Aout(ii,:);

[mr mo]

Thanks again for your help. this code is working very well for lesser than, greater then and between values, but this code doesn't tell any thing about the equality. For example this code should tell that

   c = A(4,1)

[mr mo]

This code gives this result :

 AA = [-inf;A(:,1);inf];
 Aout = hankel(AA(1:end-1),AA(end-1:end));
 ii = discretize([a,b,c,d],AA);
 out = Aout(ii,:);
 >> out

 out =

-Inf    12
  93   128
 145   180
 280   Inf

But I want this results instead :

 >> out

 out =

-Inf    12
  93   128
 145   
 280   Inf

so the third line of out means that

 c = A(4,1)

Thanks again.

[Andrei Bobrov]

ab = [a b c d]';
AA = [-inf;A(:,1);inf];

Aout = hankel(AA(1:end-1),AA(end-1:end));
ii = discretize(ab,AA);
out = Aout(ii,:);

t = bsxfun(@eq,out,ab);
out(xor(t(:,1),t(:,2)),2) = nan;

[mr mo]

This error happened .

 >> t = out == ab
 Error using  == 
 Matrix dimensions must agree.

[Andrei Bobrov]

fixed!!!

[mr mo]

Thanks again but if I have only one value for example

 f = 180

what should I do to find the equal member in A(:,1).

I tried this

 AA = [-inf;A(:,1);inf];
Aout = hankel(AA(1:end-1),AA(end-1:end));
ii = discretize(180,AA)
out = Aout(ii,:);
t = bsxfun(@eq,out,ab);
out(xor(t(:,1),t(:,2)),2) = nan;

and the result still is in the form of

 >> out

 out =

   180   220

[mr mo]

I forgot to tell that I want to try this code for the values of a, b, c and d separately.

[Andrei Bobrov]

ab = 180;
AA = [-inf;A(:,1);inf];
Aout = hankel(AA(1:end-1),AA(end-1:end));
ii = discretize(ab,AA);
out = Aout(ii,:);
t = bsxfun(@eq,out,ab);
out(xor(t(:,1),t(:,2)),2) = nan;

[mr mo]

Thank you very much. This code works very well now.

[mr mo]

@Andrei Bobrov: Hi. Thanks again for your help.

I run your above code in my matlab m-file and I must run this code in for loops, but this code is taking to much running time.

For example I run the for loops 5 times and its running time is given by Run and Time tool in Matlab in the below image.

The red digits are showing the running time of that line in second.

I must run your code 1000 times and the running time will be more than 10 hours.

Is there any possibilities to change this code to decreasing the running time?

Thanks you very much.