Multiple axis plot

Question

I have to plot some data and I need two x and y axes. The main x and y give me displacement infos, the secondary (x on top and y on the right) give me infos on energy. The issue I have is that if I make the plot window bigger the secondary axes don't resize properly and, but it is very minor, the plot title is written under the tool bar and I can see only the lower part of the letters. Someone knows how to fix the main issue on secondary axes?

The code I used for secondary axis is:

 figure(1)

%%%%voglio fare un plot tenendo fisse le dimensioni delle icone nella legenda
hplot = plot(yH(1,:),xH(1,:),'^', yC(:,1),xC(:,1),'*',yC(:,2),xC(:,2),'*',...
    yC(:,3),xC(:,3),'*',yC(:,4),xC(:,4),'*',yC(:,5),xC(:,5),'*',...
    yC(:,6),xC(:,6),'*','MarkerSize',s); % Markersize: specifys the size of the marker in points (s in questo caso)
hold on 
plot(Ymcporigine,Xmcporigine,'k-','MarkerEdgeColor','k','MarkerSize',1);  %Plot contorno MCP
hold on
plot(Yh, Xh, 'b-', 'MarkerSize', s); %Plot alone circolare
hold off

%Labe assi principali - It is necessary to give the label instructions after plot in order to avoid overlap
xlabel(gca, 'Deflessione magnetica [m]'); % label lower x axis
ylabel(gca,'Deflessione elettrica [m]');  %label left y axis 

%particles outside MCP radius won't be appear in figure
xlim([0, Rmcp])
ylim([0, Rmcp])

%%%% legenda assi principali
l=legend(hplot, 'H^+','C^+','C^{+2}','C^{+3}','C^{+4}','C^{+5}','C^{+6}', 'Location','BestOutside');
a=get(l,'children');
set(a(1:3:end),'MarkerSize',10);


%%%% doppio Asse x
%xlabel(gca, 'Deflessione magnetica [m]'); % label asse x principale

%set secondary x limit as the momentum of a H+ at distance equal to the MCP radius
% Secondo Harres y=(q*B*LB*L)/sqrt(2mEkin) ==> mv=q*B*LB*L/y
mv_max = (q*B*LB*L)/Rmcp;
%mv_max = 1;

%Layout instruction
set(gca,'Box','off');   % Turn off the box surrounding the whole axes
axesUnits=get(gca,'Units');
axesPosition = get(gca,'Position');          %# Get the current axes position
hNewAxes = axes('Position',axesPosition,...  %# Place a new axes on top...
                'Units', axesUnits,...
                'ActivePositionProperty', 'OuterPosition',...
                'Color','none',...           %#   ... with no background color
                'XAxisLocation','top',...    %#   ... located on the top
                'Ytick', [],...              %#   ... with no y tick marks
                'Xlim', [0, mv_max],...      %#   ... should define x axis scale (need to set xmax = mv_max)
                'Box','off');                %#   ... and no surrounding box

            xlabel(hNewAxes,'Momentum (H^+)');  %# Add a label to the top axis
set(gca, 'XTickLabel', num2str(get(gca,'XTick')','%g'))   

%%%%%Plot title - It is necessary to give the title instruction after secondary x axis in order to avoid overlap         
title(['Calcolo approssimato interazione ioni campo magnetico B=', num2str(B), 'Tesla']);

%%%% doppio Asse y            
%ylabel(gca,'Deflessione elettrica [m]'); %label asse y principale

%set secondary y limit as the energy of a H+ at distance equal to the MCP radius
% Secondo Harres x=(q*E*Le*L)/(2mEkin) ==> Ekin=q*E*Le*L/2mx
Le = 0.07; %Estensione del C.E.  : 70 mm
E = 100000; %campo TP.m
Ekin_max = (q*E*Le*L)/(2*m_H*Rmcp);
%mv_max = 1;

set(gca,'Box','off');   % Turn off the box surrounding the whole axes
axesUnits = get(gca,'Units');
axesPosition = get(gca,'Position');          %# Get the current axes position
hNewAxes = axes('Position',axesPosition,...  %# Place a new axes on top...
                'Units', 'normalized',...
                'ActivePositionProperty', 'OuterPosition',...
                'Color','none',...           %#   ... with no background color
                'YAxisLocation','right',...  %#   ... located on the right  
                'Ylim', [0, Ekin_max],...    %#   ... should define y axis scale (need to set ymax=Ekin_max)
                'Xtick', [],...              %#   ... with no y tick marks
                'Box','off');                %#   ... and no surrounding box

            ylabel(hNewAxes,'Energy (H^+)');  %# Add a label to the top axis
set(gca, 'YTickLabel', num2str(get(gca,'YTick')','%g'))

Answer 1

I remembered seeing this walkthrough on how to set up multiple axes in the Matlab documentation. I tried their sample code and everything resizes fine.

Where your code differs from the Matlab documentation, is that you need to define your x axis and y axis at the same time, not in two different new-axis statements. So take out your two hNewAxes statements and replace it with one that includes all the properties:

hNewAxes = axes('Position',axesPosition,...  %# Place a new axes on top...
            'Units', 'normalized',...
            'ActivePositionProperty', 'OuterPosition',...
            'Color','none',...           %#   ... with no background color
            'YAxisLocation','right',...  %#   ... located on the right  
            'XAxisLocation','top',...
            'Xlim', [0, mv_max],...
            'Ylim', [0, Ekin_max],...    %#   ... should define y axis scale (need to set ymax=Ekin_max)
            'Box','off');                %#   ... and no surrounding box

If you want to plot some of your data lines with respect to one set of axes, and some with respect to the second, then for the second set you'll have to plot them in the style laid out at the end of the walkthrough:

hl2 = line(x2,y2,'Color','k','Parent',ax2);

where the 'Parent' property tells Matlab which axes to use.

Answer 2

From the Matlab docs it looks like you should set the ActivePositionProperty as OuterPosition instead of Position. I can't reproduce the scaling issue, but setting that does seem to adjust the title position.