Find Y of the equation

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Marc Martinez Maestre
评论： Image Analyst 2020-9-23
Hey everyone,
I have a problem finding the image (y) of the equations for an specific x. I build the following "wave" that it is build with f parts of 6m per each. The first part it has two equaitons while the rest have three different funcitons per each. Every function follows teh expression a*x^2+b*x+c and I have a vector of nx3 were every column corresponds to the terms of the parabolic expression. I have performed the code for the first and last sections, but the ones in the middle I have trouble. The distribution is as follows:
-The first curve of the section, starts at the previous section, prolongates until x=L(previous section)+0.1*L(current section)
-Second curve of the current section reaches the point 0.9*L(current section)/2
-Third curve of the current section starts at 0.9*L(current section)/2 and ends at 0.9*L(current section)
The main objective is to determine the y for every x. We will enter an x, lets say for every 2m, and we have to determine the y of the equation for every 2m.
The code to determine the y I have started is the following:
y_plot=[0.246913580246914 -1.33333333333333 2.10000000000000;
-1.66666666666667 20 -57.3000000000000;
0.408163265306122 -7.10204081632653 31.1938775510204;
0.246913580246914 -4.29629629629630 18.9888888888889;
-1.66666666666667 40 -237.300000000000;
0.408163265306122 -12 88.5000000000000;
0.246913580246914 -7.25925925925926 53.6555555555556;
-1.66666666666667 60 -537.300000000000;
0.408163265306122 -16.8979591836735 175.193877551020;
0.246913580246914 -10.2222222222222 106.100000000000;
-1.66666666666667 80 -957.300000000000;
0.408163265306122 -21.7959183673469 291.275510204082;
0.246913580246914 -13.1851851851852 176.322222222222;
-1.66666666666667 100 -1497.30000000000] %coeficients of a (first column), b(second column) and c(third column)
x_div=2 %find y every 2 meters
L=[6,6,6,6,6] %beam formed by 5 sections of 6meters each
position=L(:,1);+0.1*L(:,curve)
contador_vector=1
points_x=[]
points_y=[]
for curve=2:1:(n-1) %for everysection except the first one and the last one
for position=position:x_div:position+(0.9*L(:,curve)/2) % first equation of the current section
if position<sum(L)
eq=y_plot(curve*2+contador_vector-2,1)*x^2+y_plot(curve*2+contador_vector-2,2)*x+y_plot(curve*2+contador_vector-2,3);
points_x=[points_x,position];
points_y=double([points_y,subs(eq,x,position)]);
else
end
end
for position=position:x_div:position+0.9*L(:,curve)
if position<sum(L)
eq=y_plot(curve*2+contador_vector-1,1)*x^2+y_plot(curve*2+contador_vector-1,2)*x+y_plot(curve*2+contador_vector-1,3);
points_x=[points_x,position];
points_y=double([points_y,subs(eq,x,position)]);
else
end
end
for position=position:x_div:(position+L(:,curve)+0.1*L(:,curve)-0.1*(L(:,curve)-L(:,curve+1)))
if position<sum(L)
eq=y_plot(curve*2+contador_vector,1)*x^2+y_plot(curve*2+contador_vector,2)*x+y_plot(curve*2+contador_vector,3);
points_x=[points_x,position];
points_y=double([points_y,subs(eq,x,position)]);
else
end
end
position=position+x_div;
contador_vector=contador_vector+1;
end
%
points_x'
points_y'
  2 个评论
Marc Martinez Maestre
Marc Martinez Maestre 2020-9-16
So, the loop showld find x points between 6 and 24, but it reaches 74. The main problem is how to tell matlab that:
For every one of the sections I want that the first curve that it goes between x and x2 find the y for the current position. While this position increases by 2. And if the position is bigger than x2, check in the next function. And all this funcitons are inside a vector taht contains the coefficients of the paraolic expresssion.
Image Analyst
Image Analyst 2020-9-23
Not sure what "the image (y) of the equations" is. Can you post that image?

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