Coordinates of an area graph

I've got 9 equations (correspond Y-axe) and 9 sections (correspond X-axe) from which I plot an Area Graph.

Equations:

 M1 = -F_E_1*sind(alpha_E_1+gama_1)*(x1) + F_E_2*sind(alpha_E_2+gama_1)*(x1);
 M2 = M1i_max + T1i_max*(x2) + F_D*sind(alpha_D+gama_1)*(x2);
 M3 = M2i_max + T2i_max*(x3) - F_C_1*sind(alpha_C_1-gama_1)*(x3);
 M4 = M3i_max + N3i_max*R_1*(1-cosd(phi_4)) + T3i_max*R_1*sind(phi_4);

etc

x-axe sections:

 x1p = 0         :  l1/50  : l1;
 x2p = l1        :  l2/50  : l1+l2;
 x3p = l1+l2     :  l3/50  : l1+l2+l3;
 x4p = l1+l2+l3  : ra4/50  : l1+l2+l3+ra4;

etc

Ten I plot the Area graph:

   subplot(3,1,3); % Moments
    title('Momentové složky [Nmm]')
   hold on
  area(x1pr,M1r);
  area(x2pr,M2r);
  area(x3pr,M3r); 
  area(x4pr,M4r); 
  area(x5pr,M5r); 
  area(x6pr,M6r); 
  area(x7pr,M7r); 
  area(x8pr,M8r); 
  area(x9pr,M9r);
  set(gca,'XTick', 0:50:1200);
  grid on
  colorbar

And the final result is here:

> http://tinypic.com/r/34iqovr/6

Now I need to find coordinates of the point, where is maximum.

I found maximum by:

   maximumM=max([M1 M2 M3 M4 M5 M6 M7 M8 M9 ]); %max M

So I have the y-axe value (which is › Max: 141499.264 [Nmm])

But I don't know how to find the location of this maximum. The problem is (maybe) because the plot curve is not from 1 equation, but from 9 of them. I don't know if this is problem.

Can anybody help please? I tried to find the solution here and in google but to no avail.

Answer 1

[Mahdi]

My solution would be to use the find() function. Since you have the max, you can search the data for where that value exists and then use that value to determine where it is on the x-axis:

Index1=find(y==141499.264) % Finds where in y-data the point is found
x(Index1) % Gives you the same spot with the x-value outputted.

This assumes that the x and y are in one matrix for all of the values. Otherwise, you can look through each matrix if that y-value exists.

[Son Goku ssj4]

Well, not so sure if it works.

If I write it like this:

   Index1=find([M1,M2,M3]==maximumM)      
   x(Index1)

Then the result is:

   Index1 =

    51    52

   Undefined function 'x' for input arguments of  type 'double'.

So it tells me that the x-position is between 51 and 52 column (row?) of equations M1,M2. Now how to get the x-axe coordinates :-)

The second try was the:

   Index1=find(M1==141499.264)
   x(Index1)

But the result is:

   Index1 =

   Empty matrix: 1-by-0

   Undefined function 'x' for input arguments of type 'double'.

So I don't quite understand what's happening.

Edit:

I understand your solution, but I don't know what replacement should I chose for your "y" in "y == 141499.264" The point is (I think) read the value -from graph-.

[Mahdi]

Use the first way that you suggested. I just put a number inside for illustration purposes.

Did you put all of your x-data in one matrix? As in:

x=[x1p. x2p, x3p, x4p];
x(Index1)

It might be that you are creating multiple columns and that's why it can't find the index.

[Son Goku ssj4]

Oh my GOD you're a GENIUS! :-) Thank youu!

Till later :-P

I've got two more questions but I suppose it's better to create a new thread.

Really, thank YOU very much.