conj

Complex conjugate

Syntax

*

ZC = conj(Z)

Description

ZC = conj(Z) returns the complex conjugate of the elements of Z.

Algorithm

If Z is a complex array:

*

conj(Z) = real(Z) - i*imag(Z)


continue

Pass control to the next iteration of for or while loop

Syntax

*

continue

Description

continue passes control to the next iteration of the for or while loop in which it appears, skipping any remaining statements in the body of the loop.

In nested loops, continue passes control to the next iteration of the for or while loop enclosing it.

Examples

The example below shows a continue loop that counts the lines of code in the file, magic.m, skipping all blank lines and comments. A continue statement is used to advance to the next line in magic.m without incrementing the count whenever a blank line or comment line is encountered.

*

fid = fopen('magic.m','r');
count = 0;
while ~feof(fid)
line = fgetl(fid);
if isempty(line) | strncmp(line,'%',1)
continue
end
count = count + 1;
end
disp(sprintf('%d lines',count));


contour

Two-dimensional contour plot

Syntax

*

contour(Z)
contour(Z,n)
contour(Z,v)
contour(X,Y,Z)
contour(X,Y,Z,n)
contour(X,Y,Z,v)
contour(...,LineSpec)
[C,h] = contour(...)

Description

A contour plot displays isolines of matrix Z. Label the contour lines using clabel.

contour(Z) draws a contour plot of matrix Z, where Z is interpreted as heights with respect to the x-y plane. Z must be at least a 2-by-2 matrix. The number of contour levels and the values of the contour levels are chosen automatically based on the minimum and maximum values of Z. The ranges of the x- and y-axis are [1:n] and [1:m], where [m,n] = size(Z).

contour(Z,n) draws a contour plot of matrix Z with n contour levels.

contour(Z,v) draws a contour plot of matrix Z with contour lines at the data values specified in vector v. The number of contour levels is equal to length(v). To draw a single contour of level i, use contour(Z,[i i]).

contour(X,Y,Z), contour(X,Y,Z,n), and contour(X,Y,Z,v) draw contour plots of Z. X and Y specify the x- and y-axis limits. When X and Y are matrices, they must be the same size as Z, in which case they specify a surface as surf does.

contour(...,LineSpec) draws the contours using the line type and color specified by LineSpec. contour ignores marker symbols.

[C,h] = contour(...) returns the contour matrix C (see contourc) and a vector of handles to graphics objects. clabel uses the contour matrix C to create the labels. contour creates patch graphics objects unless you specify LineSpec, in which case contour creates line graphics objects.

Remarks

If you do not specify LineSpec, colormap and caxis control the color.

If X or Y is irregularly spaced, contour calculates contours using a regularly spaced contour grid, then transforms the data to X or Y.

Examples

To view a contour plot of the function

over the range -2 x 2, -2 y 3, create matrix Z using the statements

*

[X,Y] = meshgrid(-2:.2:2,-2:.2:3);
Z = X.*exp(-X.^2-Y.^2);

Then, generate a contour plot of Z.

*

[C,h] = contour(X,Y,Z);
clabel(C,h)
colormap cool



View the same function over the same range with 20 evenly spaced contour lines and colored with the default colormap jet.

*

contour(X,Y,Z,20)



Use interp2 to create smoother contours. Also set the contour label text BackgroundColor to a light yellow and the EdgeColor to light gray.

*

Z = magic(4);
[C,h] = contour(interp2(Z,4));
h = clabel(C,h);
set(h,'BackgroundColor',[1 1 .6],...
'Edgecolor',[.7 .7 .7])