Make an array from function input and output

Question

Corey Kovacs 2018-9-1

2
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/417076-make-an-array-from-function-input-and-output

评论： KSSV 2023-10-12

I have a function that inputs velocity and angle, and outputs the distance the ball travels. Function below:

function distance = DTask1_f (v, angle)
h = 1.5;
g = 9.8;
t = linspace (0,10,1000);
x=v*cos(angle*pi/180)*t;
y=h+v*sin(angle*pi/180)*t-0.5*g*t.^2;
ind = find (x == min(x(y<0)));
fprintf ('The ball hits the ground at a distance of %5.4f meters.', x(ind));
distance = x(ind);
end

I now need to write a script that uses the function, and while using a set value for velocity, will graph angle and distance over a set of angles. My script so far:

for angle = 10:13
    v  = 4;
    y = DTask1_f (v, angle);
    x = [angle];    
      a = [x;y]
end
figure
plot(x,y)
xlabel('Angle (deg)');
ylabel('Distance (m)');
title('Ball Trajectory');

I think I need to first make an array using the angle (input) and distance (output), and then graph the array, but im not sure how to make the array. At the moment, it only gives me the last two points.

Apologies if this is a simplistic question, but thanks for the help.

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Answer 1

Stephan 2018-9-1

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/417076-make-an-array-from-function-input-and-output#answer_334988

编辑：Stephan 2018-9-1

在 MATLAB Online 中打开

Hi,

use:

angle_range = 10:1:13
for k = 1:length(angle_range)
      v = 4; 
      a(k,2) = DTask1_f (v, angle_range(k))
      a(k,1) = angle_range(k)
end
figure 
plot(a(:,1),a(:,2)) 
xlabel('Angle (deg)');
ylabel('Distance (m)');
title('Ball Trajectory');

If you want to extend or vary the range of angle or make other stepsize for angle modify first line.

Best regards

Stephan

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Stephan 2018-9-2

编辑：Stephan 2018-9-2

在 MATLAB Online 中打开

Hi,

this part has a dynamic legend now for v - No need to write it by hand everytime it is changed:

angle = 0:60;
for k = 1:length(angle)
    v  = 60;
    a(k,2) = DTask1_f (v, angle(k));
    a(k,1) = angle(k);    
end
figure
plot(a(:,1),a(:,2))
xlabel('Angle (deg)');
ylabel('Distance (m)');
legend(['v = ', num2str(v), ' m/s'])
title('Ball Trajectory');

The function should now work as you wanted it to do, with some more informations when fprinf command gives output:

function distance = DTask1_f (v, angle)
h = 1.5;
g = 9.81;
t = linspace (0,15,50000);
x=v*cos(angle*pi/180)*t;
y=h+v*sin(angle*pi/180)*t-0.5*g*t.^2;
ind = find (x == min(x(y<0)));
distance = x(ind);
if t(ind) <= 10
    fprintf ('Angle: %1.0f Degrees - The ball hits the ground at a distance of %5.4f meters in %5.4f seconds. \n',angle, x(ind), t(ind));
else
    fprintf ('NaN - Angle: %1.0f Degrees - Time: %5.4f seconds \n', angle, t(ind));
end
end

Best regards

Stephan

Corey Kovacs 2018-9-3

Thanks, that worked :)

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Answer 2

KSSV 2018-9-1

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/417076-make-an-array-from-function-input-and-output#answer_334989

在 MATLAB Online 中打开

angle = 10:13 ;
x = angle ;
y = zeros(size(angle)) ;
for i = 1:length(angle)
    v  = 4;
    y(i) = DTask1_f (v, angle(i));        
end
figure
plot(x,y)
xlabel('Angle (deg)');
ylabel('Distance (m)');
title('Ball Trajectory');