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Is there a lookup function in matlab?

Asked by John on 6 Jan 2013

Hello,

I am simulating a markov chain using the code below.

      transC = [zeros(size(T,1),1), cumsum(T,2)]; %cumulative sum of rows, we will use this to decide on the next step.
    n = 10000;
    states = zeros(1,n); %storage of states
    states(1) = 32; %start at state 1 (or whatever)
    for ii = 2:n
       %Generate a random number and figure out where it falls in the cumulative sum of that state's trasition matrix row
       [~,states(ii)] = histc(rand,transC(states(ii-1),:));
    end

It combines a transition probability matrix and a random number to return a sequence of states. e.g 1,2,4,2,5,4,3.....

However, the states are actually letter codes, e.g AA, AC, DC

I have a have a variable called 'convert' where I have a list of the states and their corresponding letter codes. For example

1 AA
2 AC
3 DC
. . 
. . 

How could I lookup the actual state names and return them in a new variable?

Thank you

0 Comments

John

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2 Answers

Answer by Image Analyst on 6 Jan 2013

Presumably your variable is a cell array where the first column is the state number (kind of unnecessary actually) and the second column is the letter code. So to get the letter code from some variable stateNumber that contains an integer, you'd simply do:

letterCode = convert{stateNumber, 2}; % convert is your cell array variable.

4 Comments

Walter Roberson on 7 Jan 2013
convert = { 1 'AA'; 2 'AC'; 3 'DC'; ... }
letterCodes = convert(states, 2);
John on 7 Jan 2013

Thank you, it works.

Is there documentation for this? I don't understand how it works, as silly as that sounds.

John

Walter Roberson on 7 Jan 2013

This is just array indexing of a cell array.

Image Analyst
Answer by Walter Roberson on 7 Jan 2013

Also you could look at containers.map

0 Comments

Walter Roberson

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