//THIS FUNCTION WILL CREATE A VARIOMETER LIKE DISPLAY OF THE INPUT DATA
//
//var1: 1xn vector             --> data to be displayd
//var2: string                 --> data unit

// in comparison with "variometer.sci" this display will show a moving y-axis,
// while the xpoly-line stays in the middle of the display.

function HeadAlt (X, Xunit, Y, Yunit);

END    = max(size(X));

fignr = 1010;       // use big numbers, so normal figures won't be affected

f = figure(fignr);
delmenu(fignr,'Datei');
delmenu(fignr,'Zusatzprogramme');
delmenu(fignr,'Editieren');
delmenu(fignr,'?');
toolbar(fignr,'off');
f.background        = 1;                // black background
f.figure_size       = [300 300];
f.figure_name       = 'Heading vs Altitude';
f.figure_position   = [700 300];


x = 90;
y = 100;                // <-- you may set the scale borders here
w = 50;                 // <-- use "w" to set the x-postion of the x-axis labe
h = 10;                 // <-- use "h" to set the y-position of they-axis label

// display actual data

for i=1:END;
    drawlater(); 
    xpoly([X(i) X(i)],[Y(i)-y/2 Y(i)+y/2],'lines',1);
    xpoly([X(i)-x/2 X(i)+x/2],[Y(i) Y(i)],'lines',1);
    a = gca();
    a.x_location = "bottom"
    a.y_location = "right";
    a.margins = [0.2,0.2,0.2,0.2];    
    a.axes_visible = ["on","on","off"];
    a.data_bounds = [X(i)-x, Y(i)-y; X(i)+x, Y(i)+y];
    a.tight_limits = "on";
    e1 = a.children(1); 
    e1.thickness = 2;  
    e2 = a.children(2); 
    e2.thickness = 2; 
    
    a.foreground                = 7;            // normal display = yellow
    a.font_foreground           = 7;
    a.font_size                 = 3;

    a.x_label.font_foreground   = 7;
    a.x_label.text = Xunit;
    a.x_label.font_angle = 0;
    a.x_label.font_size = 2;
    a.x_label.position = [X(i)-x-w Y(i)-y];

    a.y_label.font_foreground   = 7;
    a.y_label.text = Yunit;
    a.y_label.font_angle = 0;
    a.y_label.font_size = 2;
    a.y_label.position = [X(i)+x Y(i)+y+h];
    a.ticks_format = ["%d","%d",""];
    
//    a.sub_ticks = [4,1]
    
    drawnow(); 
    // for checking purpose
    // mprintf('value = %.2f, lower scale = %.2f, upper scale = %.2f \n', data(i),data(i)-y,data(i)+y);
    tstep = 50;
    xpause(tstep*1000);  // xpause counts in microseconds, tstep is for milliseconds, thatswhy factor 1000



    if  i < END
        delete(e1);
        delete(e2);
    end
end

endfunction