find
gives the indices of %T or non-zero elements
Syntax
ii = find(x) [i1,i2,..] = find(x) .. = find(x, nmax)
Arguments
- x
Vector, matrix, or hypermatrix of booleans or of numbers. All non-zero numbers are considered as %T. Sparse matrices are accepted.
- nmax
an integer giving the maximum number of indices to return. The default value is -1 which stands for "all". This option can be used for efficiency, to avoid searching all indices.
- ii
row vector of linearized indices of %T or non-zero elements, or empty matrix []
- i1, i2, ..
row vectors of directional indices, or empty matrix []
Description
If x
is a boolean matrix,
ii=find(x)
returns the vector
of indices i
for which x(i)
is "true". If no true element
found find returns an empty matrix.
[i1,i2,..]=find(x)
returns vectors of indices i1
(for rows) and i2
(for columns),..
such that x(i1(n),i2(n),..)
is "true". If no true element
found find returns empty matrices in i1
,
i2
, ...
if x
is a standard matrix or hypermatrix find(x)
is interpreted as
find(x<>0)
find([])
returns []
Examples
With input booleans:
A = [%F %T %T %F ; %T %F %F %T] find(A) find(A,2)
--> A = [%F %T %T %F ; %T %F %F %T] A = F T T F T F F T --> find(A) ans = 2. 3. 5. 8. --> find(A,2) ans = 2. 3.
With input numbers:
B = [0 -1 0 3 ; 0 -1 -0.4 0] find(B) [i, j] = find(B); [i' j']
--> B = [0 -1 0 3 ; 0 -1 -0.4 0] B = 0. -1. 0. 3. 0. -1. -0.4 0. --> find(B) ans = 3. 4. 6. 7. --> [i, j] = find(B); --> [i' j'] ans = 1. 2. 2. 2. 2. 3. 1. 4.
With an input hypermatrix of numbers:
E = grand(2,5,2,"uin",1,6) find(E < 4)
--> E = grand(2,5,2,"uin",1,6) E = (:,:,1) 1. 6. 5. 5. 4. 6. 5. 3. 4. 4. (:,:,2) 2. 4. 3. 6. 5. 5. 6. 6. 6. 4. --> find(E < 4) ans = 1. 6. 11. 15.
With an input numerical or boolean sparse matrix:
C = [0 3 7 0 9 0 0 4 0 0 5 0 6 0 1 0 3 8 ]; C = sparse(C); find(C) find(C, 4) // With input boolean sparse D = C > 4 full(D) find(D)
--> C = sparse(C); --> find(C) ans = 3. 4. 5. 7. 9. 13. 14. 15. 18. -->find(C, 4) ans = 3. 4. 5. 7. --> // With input boolean sparse --> D = C > 4 D = ( 3, 6) sparse boolean matrix ( 1, 3) T ( 1, 5) T ( 2, 5) T ( 3, 1) T ( 3, 6) T --> full(D) ans = F F T F T F F F F F T F T F F F F T -->find(D) ans = 3. 7. 13. 14. 18.
With the result of a boolean element-wise condition on texts:
beers = ["Desperados", "Leffe", "Kronenbourg", "Heineken"]; find(beers == "Leffe") find(beers == "1664")
--> find(beers == "Leffe") ans = 2. --> find(beers == "1664") ans = []
Addressing selected elements:
// a) Through their linearized indices: H = [ 0 -2 -8 4 -5 -1 -2 2 -9 5 0 1 ]; L = H; L(find(L < 0)) = -10 // b) Directly through the array of their boolean status: L = H; L(L < 0) = -10
--> // a) Through their linearized indices: --> H = [ 0 -2 -8 4 -5 -1 > -2 2 -9 5 0 1 > ]; --> L = H; --> L(find(L < 0)) = -10 L = 0. -10. -10. 4. -10. -10. -10. 2. -10. 5. 0. 1. --> // b) Directly through the array of their boolean status: --> L = H; --> L(L < 0) = -10 L = 0. -10. -10. 4. -10. -10. -10. 2. -10. 5. 0. 1.
See also
- vectorfind — locates occurences of a (wildcarded) vector in a matrix or hypermatrix
- grep — find matches of a string in a vector of strings
- findobj — find an object with specified property
- boolean — Scilab Objects, boolean variables and operators & | ~
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