is the ith element of a vector;
a(i,j) is element (i,j) of a 2-D matrix
Matlab matrices can have more than 2 dimensions.
Matlab indexing is 1-based, not 0-based like some other languages, so
the first element is a(1), not a(0).
|axis||In HW0 we discovered that
axis([xmin xmax ymin ymax]) sets scaling for the x- and y-axes.
Here we show some addition things the 'axis' command can do:
axis equal sets the aspect ratio so that equal tick mark
increments on the x-,y- and z-axis are equal in size.
axis square makes the current axis box square in size.
axis normal restores the current axis box to full size and
removes any restrictions on the scaling of the units.
This undoes the effects of axis square and axis equal.
axis off turns off all axis labeling, tick marks and background.
axis on turns axis labeling, tick marks and background back on.
rounds x to the
nearest integer towards zero.
See also floor, round, ceil
||repeat statements a specific
number of times
for i = 1:N
a(i) = sqrt(i);
||The general form of the if statement is
The statements are executed if the real part of the expression has all non-zero elements. The else and elseif parts are optional. The expressions oftent contain relational operators, such as <, <=, >, >=, ==, and ~=.
See also relop.
returns the length of vector x.
It is equivalent to max(size(x))
for non-empty arrays and 0 for empty ones.
||For vectors, max(x) is the largest element
For matrices, max(x) is a row vector containing the maximum element from each column of x.
||For vectors, min(x) is the smallest element
For matrices, min(x) is a row vector containing the minimum element from each column of x.
= num2str(x) converts the variable x into a string representation txt
with about 4 digits and an exponent if required. This is useful for
labeling plots with the title, xlabel, ylabel and text commands.
||Uniformly distributed random
numbers on the interval (0.0,1.0).
rand is a single random number
rand(m,1) is an m-by-1 column vector with m random entries
rand(m,n) is an m-by-n matrix with m x n random entries.
rand('state',0) resets the generator to its initial state.
if ( (v(i) > thresh) & (t >= tstart) & (t < tstop) )
n] = size(x) for vector/matrix x, returns the number of rows m and columns n as separate output variables.
d = size(x) returns the size as a two-element vector d = [m, m]
y, 'string') adds the text in the quotes to location (x,y) on
the current axes, where (x,y) is in units from the current plot.
lists the variables in the current workspace
|lists more information about
each variable, including size
% number of points
NPT = 6;
% generate random (x,y) coordinates
x = rand(NPT,1);
y = rand(NPT,1);
% plot the points
plot(x, y,'ro-'); hold on;
% add labels
for ipt= 1:NPT
myString = ['Point ' num2str(ipt)];
text(x(ipt)+.02 , y(ipt)+.02, myString);
% set the axis limits
axis([0 1 0 1]);