Replace array elements with strings

Hello,

I constructed an array out of three column vectors: Col1, Col2, v.

These Vectors are always equal in length, but the overall length can vary. Col1 and Col2 contain positive intergers 1 to 36, v is a double -1 to 1. The complete array displays corrolations between Polynomials, e.g: 1 (Col1 Index 1) and 3 (Col2 Index 1) corrolate with a value of -0.5 (v Index 1).

Since the Integers 1 to 36 identify the "Type" of a Zernike Polynomial, i want to replace them with the actual name of the Polynomial.

1 is called "Piston"

2 is called "Tilt X"

and so on .

In my array, or in the vectors, how can i change an integer element to a string, depending on it's value?

Thanks in advance!

Answer 1

[Jon]

In the example code below I show how to do it with 4 names, but you can expand it to however many names you have.

names = {'Piston','Tilt X', 'someName', 'yetAnotherName'}
Col1 = [1;3;4;2;1;4;3]
Col2 = [2;3;1;4;2;2;3]
v = [-0.9; 0.8; 0.2; -0.8;0.1;0.3;-0.2]

% put columns into a matrix
M = [Col1 Col2 v]

% substitute names based on indices
MwithNames = {names(Col1)' names(Col2)' v}

>> MwithNames{:,1}

ans =

7×1 cell array

{'Piston' }

{'someName' }

{'yetAnotherName'}

{'Tilt X' }

{'Piston' }

{'yetAnotherName'}

{'someName' }

>> MwithNames{:,2}

ans =

7×1 cell array

{'Tilt X' }

{'someName' }

{'Piston' }

{'yetAnotherName'}

{'Tilt X' }

{'Tilt X' }

{'someName' }

>> MwithNames{:,3}

ans =

-0.9000

0.8000

0.2000

-0.8000

0.1000

0.3000

-0.2000

[Jon]

Following up on @Steven Lord's suggestion after substituting the strings for the numerical codes (your main question) you could assign the result to a table rather than a cell array:

names = {'Piston','Tilt X', 'someName', 'yetAnotherName'}
Col1 = [1;3;4;2;1;4;3]
Col2 = [2;3;1;4;2;2;3]
v = [-0.9; 0.8; 0.2; -0.8;0.1;0.3;-0.2]

% put columns into a matrix
M = [Col1 Col2 v]

% substitute into table with names based on indices
Name1 = names(Col1)'
Name2 = names(Col2)'
M = table(Name1,Name2,v)

M =

  7×3 table

          Name1                 Name2            v  
    __________________    __________________    ____

    {'Piston'        }    {'Tilt X'        }    -0.9
    {'someName'      }    {'someName'      }     0.8
    {'yetAnotherName'}    {'Piston'        }     0.2
    {'Tilt X'        }    {'yetAnotherName'}    -0.8
    {'Piston'        }    {'Tilt X'        }     0.1
    {'yetAnotherName'}    {'Tilt X'        }     0.3
    {'someName'      }    {'someName'      }    -0.2

[Tim Richter]

Thank you very much! Didn't think it was that easy.

[Jon]

I think the data is acually in the array you call Output but it is a little hard to see. You can drill down in the workspace tab in your MATLAB IDE, or by looking at them individually, e.g typing Output{:,1} on the command line.

In any case as @Steven Lord suggested, it is probably nicer to put the mixed data (character and numeric) in a table as Ishow in my second example above

Answer 2

[Steven Lord]

I recommend using a table array to store your data of mixed types.

load patients
T = table(LastName, Age, Smoker);
head(T) % Display just the first few rows of T

ans = 8×3 table
      LastName      Age    Smoker
    ____________    ___    ______

    {'Smith'   }    38     true  
    {'Johnson' }    43     false 
    {'Williams'}    38     false 
    {'Jones'   }    40     false 
    {'Brown'   }    49     false 
    {'Davis'   }    46     false 
    {'Miller'  }    33     true  
    {'Wilson'  }    40     false 

LastName is a cell array containing char vectors. Age is a double array. Smoker is a logical array.