Find/return value from each row in a big matrix that corresponds with a condition/value

Dear All Community members,

I have a big matrix ("A") and want to return values from an array "x" for each row when a condition/value is met in matrix A.

A simplified example is given below;

A=[0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 1 1 1 1 1 1 1 1 1; 0 0.15 0.30 0.45 0.60 0.75 0.90 1 1 1 1 1 1 1 1 1 1 1 1 1 1; 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1];

x=[0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20];

Condition, c=0.9

I want to find in matrix "A" the first value that meets the condition in "c" and return the corresponding values from "x". I.e. the resulting vector shall be= 9,6,18.

Any help or tips is deeply appreciated.

Thanks in advance

Answer 1

[madhan ravi]

 Wanted = nonzeros(x .* (abs(A - c) < 1e-2))

[Erik Vabo Vatsvaag]

Let me specify, I only want the first time the value appears in each row and if the value dont appear I want closest value.

[Erik Vabo Vatsvaag]

Thank you for your help

Answer 2

[Cris LaPierre]

Is the order of the resulting vector important?

You can just do a normal equality comparison, then use any to create a logical vector displaying if the corresponding column contains at least one true value.

A=[0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 1 1 1 1 1 1 1 1 1; 0 0.15 0.30 0.45 0.60 0.75 0.90 1 1 1 1 1 1 1 1 1 1 1 1 1 1; 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1];
x=[0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20];
c=0.9;

D=A==c;
ind = any(D,1);

x(ind)

ans = 1×3    
     6     9    18

[Erik Vabo Vatsvaag]

The value migth appear several times in the array and I only want the first time or closest answer in each row.

[Erik Vabo Vatsvaag]

Thank you for your help!

[Cris LaPierre]

Closest to what?

[Erik Vabo Vatsvaag]

To the condition value

[Cris LaPierre]

A=[0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 1 1 1 1 1 1 1 1 1; 
    0 0.15 0.30 0.45 0.60 0.75 0.90 1 1 1 1 1 1 1 1 1 1 1 1 1 1; 
    0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1];
x=[0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20];
c=0.9;

D=A-c;
% You only want greater than or equal to, so set everything less than to a large positive value
D(D<0)=999;
[~,ind] = min(D,[],2)

x(ind)

Answer 3

[Erik Vabo Vatsvaag]

Sorry, let me specify.

I only want the first value equal to or bigger than c. Both your answers will be wrong if 0.9 appears more than once per row.

Thank you so much for your help!

Answer 4

[Bruno Luong]

"Let me specify, I only want the first time the value appears in each row and if the value dont appear I want closest value."

Then use MIN rather than FIND, and no need to fix emperically the tolerance.

c = 0.9;
[~,col] = min(abs(A-c),[],2);
x(col)