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Appendix. The HELP document
NEWS MATLAB NEWS dated 3/21/82.
Normalization of some eigenvectors associated with multiple
eigenvalues has been altered to reduce overflow.
New features added since the November 1980 printing of the
Users' Guide include six element-by-element operations
.* ./ .\ .*. ./. .\., and
DIARY, EDIT, KRON, MACRO, PLOT, RAT, TRIL, TRIU.
Some additional capabilities have been added to
EXIT, RANDOM, RCOND, SIZE and SVD.
INTRO Welcome to MATLAB.
Here are a few sample statements:
A = <1 2; 3 4>
b = <5 6>'
x = A\b
<V,D> = eig(A)
norm(A-V*D/V)
help \
help eig exec('demo',7)
For more information, see the MATLAB Users' Guide.
HELP HELP gives assistance.
HELP HELP obviously prints this message.
To see all the HELP messages, which include all the
functions and operators available in this Archimedes
version of MATLAB, list the file HLP.
< < > Brackets used in forming vectors and matrices.
[ ] can also be used for this purpose.
<6.9 9.64 SQRT(-1)> is a vector with three elements
separated by blanks. <6.9,9.64,sqrt(-1)> is the same
thing. <1+I 2-I 3> and <1 +I 2 -I 3> are not the
same; the first has three elements, the second has five.
<11 12 13; 21 22 23> is a 2 by 3 matrix - the semicolon
ends the first row.
Vectors and matrices can be used inside < > brackets.
<A B; C> is allowed if the number of rows of A equals the
number of rows of B and the number of columns of A plus the
number of columns of B equals the number of columns of C.
This rule generalizes in a hopefully obvious way to allow
fairly complicated constructions.
A = < > stores an empty matrix in A, thereby removing it
from the list of current variables.
For the use of < and > on the left of the = in multiple
assignment statements, see LU, EIG, SVD and so on.
In WHILE and IF clauses,
<> means less than or greater than, i.e. not equal,
< means less than,
> means greater than,
<= means less than or equal,
>= means greater than or equal.
For the use of > and < to delineate macros, see MACRO.
> See <. Also see MACRO.
( ( ) used to indicate precedence in arithmetic
expressions in the usual way, to enclose arguments of
functions in the usual way, and to enclose sub-scripts
of vectors and matrices in a manner somewhat more general
than the usual way. If X and V are vectors, then X(V) is
<X(V(1)),X(V(2)), ... ,X(V(N)>. The components of V are
rounded to nearest integers and used as subscripts. An
error occurs if any such subscript is less than 1 or
greater than the dimension of X.
Some examples:
X(3) is the third element of X.
X(<1 2 3>) is the first three elements of X,so is
X(<SQRT(2),SQRT(3),4*ATAN(1)>).
If X has N components, X(N:-1:1) reverses them.
The same indirect subscripting is used in matrices: if V
has M components and W has N components, then A(V,W) is
the M by N matrix formed from the elements of A whose
subscripts are the elements of V and W. For example,
A(<1,5>,:) = A(<5,1>,:) interchanges rows 1 and 5 of A.
) See (.
= Used in assignment statements and to mean equality in
WHILE and IF clauses.
. Decimal point. 314/100, 3.14 and .314E1 are all the same.
Element-by-element multiplicative operations are obtained
using .* , ./ , or .\ . For example, C = A./B is the
matrix with elements c(i,j)=a(i,j)/b(i,j).
Kronecker tensor products and quotients are obtained with
.*. , ./. and .\. See KRON.
Two or more points at the end of the line indicate
continuation. The total line length limit is 1024
characters.
, Used to separate matrix subscripts and function
arguments. Used at the end of FOR, WHILE and IF clauses.
Used to separate statements in multi-statement lines. In
this situation, it may be replaced by semicolon to suppress
printing.
; Used inside brackets to end rows. Used after an
expression or statement to suppress printing. See SEMI.
\ (backslash) Matrix left division. A\B is roughly the
same as INV(A)*B, except it is computed in a different
way. If A is an N by N matrix and B is a column vector
with N components, or a matrix with several such columns,
then X = A\B is the solution to the equation A*X = B
computed by Gaussian elimination. A warning message is
printed if A is badly scaled or nearly singular. A\EYE
produces the inverse of A.
If A is an M by N matrix with M < or > N, and B is a column
vector with M components, or a matrix with several such
columns, then X = A\B is the solution in the least squares
sense to the under- or over-determined system of equations
A*X = B. The effective rank, K, of A is determined from
the QR decomposition with pivoting. A solution X is
computed which has at most K non-zero components per
column. If K < N this will usually not be the same
solution as PINV(A)*B. A\EYE produces a generalized
inverse of A.
If A and B have the same dimensions, then A.\B has elements
a(i,j)\b(i,j). See also KRON.
[Also, see EDIT.]
/ (slash) Matrix right division. B/A is roughly the
same as B*INV(A). More precisely, B/A = (A'\B')'.
See \ (backslash).
IF A and B have the same dimensions, then A./ B has
elements a(i,j)/b(i,j). See also KRON.
Two or more slashes together on a line indicate a logical
end of line. Any following text is ignored.
' Transpose. X' is the complex conjugate transpose of X.
Quote. 'ANY TEXT' is a vector whose components are the
MATLAB internal codes for the characters. A quote within
the text is indicated by two quotes.
See DISP and FILE.
+ Addition. X + Y. X and Y must have the same
dimensions.
- Subtraction. X - Y. X and Y must have the same
dimensions.
* Matrix multiplication. X * Y. Any scalar (1 by 1
matrix) may multiply anything. Otherwise, the number of
columns of X must equal the number of rows of Y.
Element-by-element multiplication is obtained with X.*Y.
The Kronecker tensor product is denoted by X.*.Y .
Powers. X**p is X to the power p; p must be a scalar.
For a matrix X, see FUN. N.B. Later versions of MATLAB
use X^p for X to the power p; this is not recognised and
produces an error in this version.
: Colon. Used in subscripts, FOR iterations, and
possibly elsewhere.
J:K is the same as <J,J+1, ... ,K>.
J:K is empty if J > K.
J:I:K is the same as <J,J+I,J+2I, ... ,K>.
J:I:K is empty if I > 0 and J > K,
or if I < 0 and J < K.
The colon notation can be used to pick out selected rows,
columns and elements of vectors and matrices.
A(:) is all the elements of A, regarded as a single column.
A(:,J) is the J-th column of A.
A(J:K) is A(J), A(J+1), ... , A(K).
A(:,J:K) is A(:,J), A(:,J+1), ... ,A(:,K), and so on.
For the use of the colon in the FOR statement, see FOR.
ABS ABS(X) is the absolute value, or complex modulus, of
the elements of X.
ANS Variable created automatically when expressions are
not assigned to anything else.
ATAN ATAN(X) is the arctangent of X. See FUN.
BASE BASE(X,B) is a vector containing the base B
representation of X.
This is often used in conjunction with DISPLAY.
DISPLAY(X,B) is the same as DISPLAY(BASE(X,B)).
For example, DISP(4*ATAN(1),16) prints the hexadecimal
representation of pi.
CHAR CHAR(K) requests an input line containing a single
character to replace MATLAB character number K in the
following table. For example, CHAR(45) replaces backslash.
CHAR(-K) replaces the alternate character number K.
K character alternate name
0 - 9 0 - 9 0 - 9 digits
10 - 35 A - Z a - z letters
36 blank
37 ( ( lparen
38 ) ) rparen
39 ; ; semi
40 : | colon
41 + + plus
42 - - minus
43 * * star
44 / / slash
45 \ $ backslash
46 =