EGR 115 Introduction to Computing for Engineers 2D Plotting – Part I Wednesday 17 Sept 2014 EGR 115 Introduction to Computing for Engineers

EGR 115 Introduction to Computing for Engineers

2D Plotting – Part I

Wednesday 17 Sept 2014 EGR 115 Introduction to Computing for Engineers

http://www.erau.edu/

Lecture Outline


• 2D Plotting Additional plotting features

Slide 2 of 13


2D PlottingAdditional Plotting Features – LineSpec Review


• Review of Line Specifications

• For Example:>> x=0:0.1:pi;>> plot(x, sin(x), ‘k>:')

Line Color Marker Line Style b blue . point - solid g green o circle : dotted r red x x-mark -. dashdot c cyan + plus -- dashed m magenta * star (none) no line y yellow s square k black d diamond w white v triangle (down) ^ triangle (up) < triangle (left) > triangle (right) p pentagram h hexagram

0 0.5 1 1.5 2 2.5 3 3.50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Slide 3 of 13


2D PlottingAdditional Plotting Features – Log Scales


• Logarithmic Scales Consider the low-pass filter

with transfer function:

o where, is the filter cut-off frequency and f the frequency in Hz.

Assuming , plot the attenuation () of the filter for 0 < f < 1,000 Hz.

>> f = 0:1000;>> fc = 200;>> G = 1 ./ (1 + 1i*(f/fc));>> plot(f, sqrt(G .* conj(G)))>> xlabel('Freq in Hz');>> ylabel('Attenuation')>> title('Attenuation of a Low-Pass Filter')

1

( )1 / c

G fj f f

*( ) ( ) ( )G f G f G f

0 100 200 300 400 500 600 700 800 900 10000.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Freq in Hz

Att

enua

tion

Attenuation of a Low-Pass Filter

Linear / Linear plot

Slide 4 of 13


100

101

102

103

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Att

enua

tion

Freq in Hz




A log / linear plot>> semilogx(f, sqrt(G .* conj(G)))>> xlabel('Freq in Hz');>> ylabel('Attenuation')>> title('Attenuation of a Low-Pass Filter')

Cut-off freq of 200 Hz

Slide 5 of 13


100

101

102

103

10-15

10-10

10-5

100

Freq in Hz

Att

enua

tion

in d

b




• Plot the attenuation in db = 20 log10(?) A log / log plot>> loglog(f, (sqrt(G .* conj(G))).^20)>> xlabel('Freq in Hz');>> ylabel('Attenuation in db')>> title('Attenuation of a Low-Pass Filter')>> grid

log( ) log( )aa b b

Cut-off freq of 200 Hz at

-3 db

Slide 6 of 13


2D PlottingAdditional Plotting Features – Plot Limits


• Controlling the limits for the x and y axes of a plot

axis([xmin xmax ymin ymax]) Sets the limits for the x- and y-axis of the current plot

axis tight Sets the axis limits to the range of the data

axis equal Sets the aspect ratio so that the data units are the same

axis off turns off all axis lines, tick marks, and labels

axis square makes the current axes region square

xlim([xmin xmax]) Sets only the x-axis limits

ylim([ymin ymax]) Sets only the y-axis limits

Slide 7 of 13


2D PlottingAdditional Plotting Features – Plot Limits


0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

0.02

0.04

0.06

0.08

0.1

0.12

0.14Default plot

0 0.5 1 1.5 2 2.50

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2Using: axis([0 2.5 0 0.2])

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

0.02

0.04

0.06

0.08

0.1

0.12

Using: axis tight

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

Using: axis equal

0 0.5 1 1.5 20

0.02

0.04

0.06

0.08

0.1

0.12

0.14Using: axis square

0 0.5 1 1.5 2 2.50

0.02

0.04

0.06

0.08

0.1

0.12

0.14Using: xlim([0 2.5])

Data units the samei.e., 0.2 in x = 0.2 in y Square aspect ratio

Slide 8 of 13


2D PlottingAdditional Plotting Features – Left / Right Axis Plots


• Plotting with Both Left and Right Side Axes A Hwk problem with speed and position (MATLAB code)

0 1 2 3 4 5 6 7 8 9 100

200

400

600

800

1000

1200

1400

1600

1800

2000Plot of Height and Speed vs Time

Time (s)

Hei

ght

(m)a

nd S

peed

(m

/s)

height

speed

0 1 2 3 4 5 6 7 8 9 100

1000

2000Plot of Height and Speed vs Time

Time (s)

Hei

ght

(m)

0 1 2 3 4 5 6 7 8 9 10100

150

200

Spe

ed (

m/s

)

height

speed

plotyy(time, height , time, speed)plot(time, height , time, speed)

Labeling the right axis can be tricky!!Slide 9 of 13


2D PlottingAdditional Plotting Features – Creating Multiple Figures


• Issuing multiple plot commands will result in overwriting the prior plot window:

The “figure” command creates a new plot window

>> t = 0:0.1:2*pi;>> plot(t, sin(t), 'b')>> plot(t, cos(t), 'r')

Overwrites the Prior Plot

>> t = 0:0.1:2*pi;>> figure(1)>> plot(t, sin(t), 'b')>> figure(2)>> plot(t, cos(t), 'r')

Creates two Plot Windows

Slide 10 of 13


0 2 4 6 8-1

-0.5

0

0.5

1Subplot 1: Sin()

0 2 4 6 8-1

-0.5

0

0.5

1Subplot 2: Cos()

0 2 4 6 8-1

-0.5

0

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1Subplot 3: Sin(2)

0 2 4 6 8-1

-0.5

0

0.5

1Subplot 4: Cos(2)

2D PlottingAdditional Plotting Features – SubPlots


• We can also place multiple plots in a single figure:

Subplot(num_rows, num_cols, position)

Position#1 Position#2

Position#3 Position#4

%% An in class example of subplotst = 0:0.1:2*pi; % Array of angles (rad) figure(1); % Open a new figure subplot(2, 2, 1); % Subplot#1 at position 1,1plot(t, sin(t)); % Plot sin(theta)title('Subplot 1: Sin(\theta)') subplot(2, 2, 2); % Subplot#2 at position 1,2plot(t, cos(t)); % Plot cos(theta)title('Subplot 2: Cos(\theta)') subplot(2, 2, 3); % Subplot#1 at position 2,1plot(t, sin(2*t)); % Plot sin(2 theta)title('Subplot 3: Sin(2\theta)') subplot(2, 2, 4); % Subplot#2 at position 2,2plot(t, cos(2*t)); % Plot cos(2 theta)title('Subplot 4: Cos(2\theta)')

Slide 11 of 13


2D PlottingAdditional Plotting Features – SubPlots


• Create the following plot:

0 1 2 3 4 5 6 7-1

-0.5

0

0.5

1Subplot 1: Sin()

0 1 2 3 4 5 6 7-1

-0.5

0

0.5

1Subplot 2: Cos()

Slide 12 of 13


Next Lecture


• Annotation of Plots• Polar, Bar, Pie, … Plots

Slide 13 of 13


Documents

EGR 115 Introduction to Computing for Engineers 2D Plotting – Part I Wednesday 17 Sept 2014 EGR 115 Introduction to Computing for Engineers