Matlab function/code similar to excel vlookup?

I am calculating a range of values, x, from a loop and require them to be matched to the corresponding x value from given data and then select the given x value's associated value, y.

Is there a function/code that can do this?

Thanks

Ewan

Answer 1

[Cedric]

Look at this example:

 >> x = [1, 4, 2, 5, 3, 7, 6] ;   % Fake x and y.
 >> y = x + 10 ;

 >> for k = 1 : 7,  y(x == k),  end
 ans =
     11
 ans =
     12
 ans =
     13
 ans =
     14
 ans =
     15
 ans =
     16
 ans =
     17

Here, we use logical indexing to extract the relevant element of y, as illustrated below for finding the y corresponding to x equals 5:

 >> x == 5
 ans =
     0     0     0     1     0     0     0
 >> class(x)
 ans =
     double

The test of equality (relational operator) returns a vector of logicals that whose elements indicate whether the test is true (1) or false (0). This vector can be used for indexing y (look at logical indexing in the doc if needed):

 >> y(x == 5)
 ans =
    15

Answer 2

[vivek cheruvu]

Hello,

I have two sets of data (voltage, energy) each has 4778 values. For every value of energy, I want the corresponding voltage. To be short, I want to implement a lookup table function in Matlab script. These values are used within FOR loop. Please help me out with this, the above code is throwing me error "empty matrix 0x1".

[Walter Roberson]

I just tested Cedric's code as posted and it is working fine.

However, Cedric's code relies upon the value being looked up being bit-for-bit exactly equal to one of the stored x values. If you do not have bit-for-bit exact matches then you need to define how you want the lookup to proceed.

You should probably look at interp1()