How to edit the red "+" marks on the Nyquist plot

Is there a way to change the thickness and color of the red + marks that appear when drawing a Nyquist diagram?

[Aquatris]

are you talking about the red + sign on the -1 point?

Answer 1

[Voss]

H = tf([2 5 1],[1 2 3]);
nyquist(H)

h = findall(gcf(),'Type','line')

h = 
  5x1 Line array:

  Line
  Line
  Line
  Line
  Line

mkr = get(h,'Marker')

mkr = 5x1 cell array
    {'+'   }
    {'none'}
    {'none'}
    {'none'}
    {'none'}

h = h(strcmp(mkr,'+'));

h.LineWidth = 5;
h.Color = [0 1 0];
h.MarkerSize = 20;

[ayumi obitsu]

Mr. Voss

Thank you for your reply.

I was able to successfully change the color and thickness of the + mark.

h = h(strcmp(mkr,'+'));

What does this operation do?

[Voss]

You're welcome!

Regarding the line of code you asked about, before that line is executed, h contains all the line objects in the figure. That line of code compares the marker of each line object to '+' and keeps only the line objects whose marker is '+', so that afterwards h contains only those line objects whose marker is '+'.

[Steven Lord]

A slightly simpler approach would be to directly findobj all objects whose Marker property is '+'.

H = tf([2 5 1],[1 2 3]);
nyquist(H)

h = findall(gcf(),'Marker', '+')

h = 
  Line with properties:

              Color: [1 0 0]
          LineStyle: '-'
          LineWidth: 0.5000
             Marker: '+'
         MarkerSize: 6
    MarkerFaceColor: 'none'
              XData: -1
              YData: 0
              ZData: -10

  Use GET to show all properties

The properties (specifically Color, Marker, XData, and YData) indicate that this is the "line" that is the red + symbol. This avoids the strcmp call.

Answer 2

[Umar]

Hi Ayumi,

To change the thickness and color of the red + marks in a Nyquist diagram, you can modify the properties of the plot after generating it. Below is an example illustrating how to achieve this customization. So, first, I will create a transfer function G as an example.Next, generate the Nyquist plot using the nyquist function. Afterwards, access the current figure handle and find all lines with a red color (indicating the + marks). Finally, we set the line width to 2 and change the color to blue for better visibility.

>> % Create a transfer function G = tf([1], [1, 2, 1]);

% Generate the Nyquist plot figure; nyquist(G);

% Access the current figure and set properties of the red + marks h = gcf; % Get current figure handle redPlusMarks = findall(h, 'Type', 'line', 'Color', [1 0 0]); % Find red lines set(redPlusMarks, 'LineWidth', 2); % Set line width to 2 set(redPlusMarks, 'Color', [0 0 1]); % Set color to blue

Please see attached plot as reference.

By following this approach, you can easily customize the appearance of the red + marks in Nyquist diagrams according to your preferences.

[ayumi obitsu]

Mr.Umar

Thank you for your reply.

I was able to successfully change the color and thickness of the + mark.