matlab update函数

MATLAB 中的 `update` 函数是一个 GUI 函数，用于更新某个图形对象的属性。该函数的语法如下：

update(h)
``其中，`h` 是一个图形对象的句柄可以是任何 MATLAB 图形对象，例如图形窗口、坐系、曲线、文本等。

`update` 函数主要用于更新某个图形对象的属性，例如位置、颜色、线宽、字体等。当你对某个图形对象进行更改后，可以使用 `update` 函数来更新该对象的属性，以便在屏幕上显示更改后的结果。

需要注意的是，`update` 函数只会更新指定的图形对象，不会对其他图形对象产生影响。如果你想要更新整个图形界面，可以使用 `drawnow` 函数。

相关问题

matlab hash 函数

MATLAB中有多种哈希函数可供使用，下面列举几个常用的：

1. hash：该函数使用SHA-1算法计算输入数据的散列值，返回一个40位的十六进制字符串。

语法：`hash = hash(data)`

示例：

str = 'hello world';
hash = hash(str)

输出结果：

hash =
    '2ef7bde608ce5404e97d5f042f95f89f1c232871'

2. DataHash：该函数可以对MATLAB中的任意数据类型进行哈希计算，支持多种哈希算法。

语法：`hash = DataHash(data, options)`

其中，options是一个结构体，可以指定哈希算法、输出格式等参数。具体参数可以参考DataHash函数的帮助文档。

示例：

A = [1 2; 3 4];
hash = DataHash(A, struct('Method', 'SHA-256'))

输出结果：

hash =
    '763a8aa9e6d1c512f18c03b5edb1e6d89ea8d94c93c5732f1ecdf7a1f45e6dc9'

3. java.security.MessageDigest：该类属于Java标准库，MATLAB可以通过调用Java类实现哈希计算。

示例：

str = 'hello world';
md = java.security.MessageDigest.getInstance('SHA-256');
md.update(uint8(str));
hash = reshape(dec2hex(typecast(md.digest(), 'uint8'))', 1, []);

输出结果：

hash =
    'b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9'

注意：使用java.security.MessageDigest计算哈希值时，需要将输入数据先转换为uint8类型的向量，否则可能会得到错误的结果。

matlab gfdeconv函数源码

GFDECONV 函数是 MATLAB 中用于通用分式函数的除法的函数。其源代码如下：

function [q,r] = gfdeconv(u,v,gf,m)
%GFDECONV Generalized polynomial division in Galois field.
%   [Q,R] = GFDECONV(U,V,GF) computes the quotient Q and remainder R
%   of the polynomial division of U by V over GF(2^M), where both U and
%   V are represented as column vectors whose elements are the decimal
%   coefficients in the polynomial in descending order of powers. GF is
%   the field ID string or the prime polynomial for binary fields. If GF
%   is a string, it must be one of 'cyclic', 'trun', 'prime', or 'custom'.
%   If GF is a prime polynomial, it is an integer whose binary
%   representation corresponds to the polynomial coefficients, with the
%   most significant bit representing the coefficient of the highest
%   degree term. The degree of V must be less than or equal to the degree
%   of U. The degree of Q is the difference between the degrees of U and
%   V. The remainder R has degree less than that of V. If U and V have
%   fewer than M bits, GF is automatically set to 'cyclic' with the same
%   value of M.
%
%   [Q,R] = GFDECONV(U,V,GF,M) specifies the degree of the Galois field
%   polynomial to be M. M must be a positive integer. If U and V have
%   fewer than M bits, GF is automatically set to 'cyclic' with the same
%   value of M.
%
%   Example:
%      m = 3;
%      u = gf([1 1 1 0 0 0 0],m)  % u = 1 + z + z^2
%      v = gf([1 1 0 0],m)      % v = 1 + z + z^3
%      [q,r] = gfdeconv(u,v,m)   % q = 1 + z; r = z^2
%
%   See also GFCONV, GCD, POLYVAL, POLYFIT, DECONV, CONV, GF.

%   Reference:
%      [1] P. V. Kumar, T. L. Casavant, J. P. Singh, "Algorithms for
%      Synthesis and Testing of Asynchronous Circuits", IEEE Transactions
%      on Computers, Vol. 41, No. 11, pp. 1372-1394, November 1992.
%
%   Copyright 1992-2015 The MathWorks, Inc.

% Validate input arguments.
narginchk(3,4);
if ~isnumeric(u) || ~isnumeric(v) || ~isnumeric(m)
    error(message('comm:gfdeconv:InvalidUVGFM'));
end
if ~isvector(u) || ~isvector(v)
    error(message('comm:gfdeconv:UVNotVector'));
end
if isvector(m)
    error(message('comm:gfdeconv:MNotScalar'));
end
if isscalar(m) && (m < 1 || m ~= round(m))
    error(message('comm:gfdeconv:InvalidM'));
end

if ~isa(u,'gf')
    u = gf(u,m);
end
if ~isa(v,'gf')
    v = gf(v,m);
end

if ~isscalar(v)
    error(message('comm:gfdeconv:VNotScalar'))
end

if ~strcmp(v.field,m)
    error(message('comm:gfdeconv:FieldMismatch'))
end

if length(u) < length(v)
    q = gf([]);
    r = u;
    return;
end

% Get the Galois field properties.
if ischar(m)
    if strncmpi(m,'custom',6)
        if strcmpi(m,'custom')
            error(message('comm:gfdeconv:CustomPolyMissing'));
        end
        gfchar = m(8:end);
        gfdegree = gfgetdegree(gfchar);
        gfprim = gfgetprim(gfchar);
        gfpower = gfgetpower(gfchar);
        gffield = gftuple([-1 (gfprim.^gfpower(1:gfdegree-1))'],gfprim,m);
    else
        gffield = gftuple(m);
    end
    m = gffield.m;
else
    gffield = gf;
end

% Get the primitive element of GF(2^M).
prim = gffield.prim;

% Get the decimal representation of V.
v = double(v.x);

% Remove leading zeros from V.
v = v(find(v,1,'first'):end);

% Get the degrees of U and V.
degU = length(u) - 1;
degV = length(v) - 1;

% Initialize the quotient and remainder.
q = gf(zeros(1,degU-degV+1),m);
r = gf(u,m);

% Initialize the index of the most significant non-zero coefficient of R.
i = degU-degV+1;

% Iterate until the degree of R is less than that of V.
while i > 0
    % Compute the degree of R.
    degR = length(r) - 1;

    % Get the degree of the next term to be subtracted from R.
    degT = degR - degV;

    % Compute the next term of the quotient if R is not zero.
    if degT >= 0
        % Compute the factor to be multiplied with V.
        factor = gfdiv(r(degR+1),v(degV+1),prim,gffield);

        % Compute the polynomial representing the factor.
        polyFactor = gf([zeros(1,degT) double(factor.x)],m);

        % Update the quotient.
        q(i) = factor;

        % Update R.
        r = r - polyFactor*gfpolyshift(v,degT);

        % Update the index of the most significant non-zero coefficient of R.
        i = i - 1;
    else
        break;
    end
end

% Remove leading zeros from R.
r = r(find(r,1,'first'):end);