Update dot in plot according to sliders

As stated in the question, I'm trying to draw a dot along a plotted graph. The graph is simulating the normalized throughput of the SAW-ARQ and it depends on 3 variables, which can be changed with 1 slider each. The dot should represent the result of the equation with the given parameters (from the sliders).

So far, I have managed to obtain the values from the sliders with a listener, but when I try to draw it within the callback of the listener, the old positions of the dot are not removed (as can be seen in the screenshot).

I want the graph to have the constant line, which doesn't have to do anything with the sliders and a dot, which is on the position according to the slider values. This dot should basically overwrite the old dot on the new position, so only 1 dot at a time.

I have also tried using the set command within the callback, but it returned an error, so I thought this was the easier way.

You can find my code below:

clear all; close all;

a = logspace(-1,3);
p = zeros(1,50);

% calculation with given a
for i = 1:length(a)
    S(i) = calcS(a(i),p(i));
end

f = figure;
semilogx(a,S); hold on;

title('SAW-ARQ performance');
% xlabel({'a','increasing data rate \rightarrow','increasing distance \rightarrow','\leftarrow increasing PDU size'});
xlabel({'a','','','','',''});
ylabel('normalized throughput'); grid on;

sliderControl(f);

% d ... distance; v ... velocity/speed; L ... PDU length; R ... data rate
function a = calcA(d,v,L,R)
    a = (d/v)/(L/R);
end

% p ... error probability
function S = calcS(a,p)
    S = (1-p)/(1+2*a);
end

function [] = sliderControl(f)
    guidata(f,struct('d',1000,'dr',64000,'pdu',1000));

      % Distance
      sliderDistance = uicontrol('Parent',f,'Style','slider','Position',[160,60,360,23],...
          'String','distance','value',1000,'min',0,'max',10e6);
      uicontrol('Parent',f,'Style','text','Position',[10,56,140,23],...
          'String','Distance [0m...1000km]','BackgroundColor',f.Color);
      addlistener(sliderDistance,'ContinuousValueChange',@updateGraph);

      % Data rate
      sliderDataRate = uicontrol('Parent',f,'Style','slider','Position',[160,35,360,23],...
          'String','datarate','value',64000,'min',0,'max',10e8);
      uicontrol('Parent',f,'Style','text','Position',[10,31,140,23],...
          'String','Data rate [0bit/s...1Gbit/s]','BackgroundColor',f.Color);
      addlistener(sliderDataRate,'ContinuousValueChange',@updateGraph);

      % PDU size
      sliderPDU = uicontrol('Parent',f,'Style','slider','Position',[160,10,360,23],...
          'String','pdu','value',1000,'min',0,'max',1500);
      uicontrol('Parent',f,'Style','text','Position',[10,6,140,23],...
          'String','PDU length [0bit...1500bit]','BackgroundColor',f.Color);
      addlistener(sliderPDU,'ContinuousValueChange',@updateGraph);
  end

function [] = updateGraph(varargin)
    hObj = varargin{1};  
    data = guidata(hObj);

      if strcmp(get(hObj,'String'),'distance')
          % d = get(hObj,'Value');
          data.d = hObj.Value;
          guidata(hObj,data);
      elseif strcmp(get(hObj,'String'),'datarate')
          % dr = get(hObj,'Value');
          data.dr = hObj.Value;
          guidata(hObj,data);
      else
          % pdu = get(hObj,'Value');
          data.pdu = hObj.Value;
          guidata(hObj,data);
      end

      % Calculation
      a = logspace(-1,3);
      tempA = calcA(data.d,3e8,data.pdu,data.dr);
      tempS = calcS(tempA,0.00);

      if tempA > a(1) && tempA < a(length(a))       
          plot(tempA,tempS,'or','MarkerSize',5,'MarkerFaceColor','r');
          pause(.5);
      end
  end

Answer 1

[KevinM]

I managed to solve the problem by myself, inspired by your answer.

Here is what I did:

• Create an empty plot with handle for the dot after the line plot

dotPlot = plot(NaN,NaN,'or','MarkerSize',5,'MarkerFaceColor','r');

• Change the callback-method for all 3 listeners so they have a third parameter for the plot

addlistener(sliderDistance,'ContinuousValueChange',@(src,evnt)updateGraph(src,evnt,dotPlot));

• Use set to update the dot according to the sliders in the callback

% Calculation
    a = logspace(-1,3);
    tempA = calcA(data.d,3e8,data.pdu,data.dr);
    tempS = calcS(tempA,0.00);

      if tempA > a(1) && tempA < a(length(a))
          set(dotPlot,'XData',tempA,'YData',tempS);
          pause(.2);
      end

Answer 2

[Greg]

I forget which release introduced MarkerIndices for plots, but I think that's exactly what you're going for. You don't need an additional plot when using MarkerIndices. Store the handle from the original plot, then just update inside your slider callback:

% Code to calculate plotted array indices to receive markers
newIndices = ...
hPlot.MarkerIndices = newIndices;