how can you plot a matrix row vs row using a for loop

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Will 2013-3-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/66378-how-can-you-plot-a-matrix-row-vs-row-using-a-for-loop

We were given 5 springs and had to put 3 different masses on each spring and then measure the displacement for each spring for each mass (3 masses & 3 displacements per spring).

% Masses for each Spring [g]:          % 3 masses per spring
S1_M=[10 20 30];
S2_M=[20 30 50];
S3_M=[50 100 150];
S4_M=[100 200 300];
S5_M=[100 200 300];
% Displacement for each Spring [in]:        % Displacements for each mass
S1_D=[1.35 2.95 4.45];
S2_D=[1.05 1.65 2.85];
S3_D=[1.1 2.55 3.9];
S4_D=[1.75 4.1 6.3];
S5_D=[1.25 2.9 4.45];
% Convert displacement from [in] to [m]:
S1_D=S1_D*0.0254;
S2_D=S2_D*0.0254;
S3_D=S3_D*0.0254;
S4_D=S4_D*0.0254;
S5_D=S5_D*0.0254;
% Convert mass[g] to force[N]:
S1_M=S1_M*0.0098;
S2_M=S2_M*0.0098;
S3_M=S3_M*0.0098;
S4_M=S4_M*0.0098;
S5_M=S5_M*0.0098;
% Create a single matrix for all 5 springs:
Disp=[S1_M;S1_D;S2_M;S2_D;S3_M;S3_D;S4_M;S4_D;S5_M;S5_D];

I know im right up until this point.

Then it says: in a function, use polyfit to determine the stiffness of each individual spring. Use a for loop within the function to accomplish these caculations. There are 5 springs and we are supposed to plot the force versus the displacement for each individual spring in a new figure. Below is how I started it, am I even doing this right?

? - means I don't know what variable to put there

 % Create a for loop using polyfit to calculate the spring constants:
function[?]=?
[r,c]=size(Disp)
for i=1:1:r
  for j=1:1:c                                  %im missing the ployfit part
      plot(Disp(?),Disp(?),'bo')                in the for loop
  end    
end

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Daniel Shub 2013-3-8

http://www.mathworks.com/matlabcentral/answers/29922-why-your-question-is-not-urgent-or-an-emergency

You are essentially asking I to do your homework for you. That is not appreciated. Edit the question to show what you have tried, otherwise I will keep closing the question.

Will 2013-3-8

Im sorry Daniel and Walter. I didnt know the policy and didnt mean to offend anyone. that was not my intentions at all. im stuck and dont know how to move on form here. i want nobody to do this for me. i just need help using polyfit to plot row vs row

sorry my my actions offending yal any help truly is greatly appreciated

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回答（1 个）

Image Analyst 2013-3-8

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/66378-how-can-you-plot-a-matrix-row-vs-row-using-a-for-loop#answer_77934

编辑：Image Analyst 2013-3-8

Assuming you have one mass at a time hanging vertically down, where the other end of the spring is attached to the ceiling, you can say force = k*distance = mass*acceleration = mass*g. So k = force / distance. You have the force and you have the distance so you just need to make up the 3 k's I would guess. Though I don't know why you need polyfit instead of just averaging the 3 k's. Then you do that for each of the 5 springs.

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Will 2013-3-8

在 MATLAB Online 中打开

SP=spring M=mass(Force) D=Displacement

the problem says the format of the matrix has to be:

SP1-M1 SP1-M2 SP1-M3
SP1-D1 SP1-D2 SP1-D3
SP2-M1 SP2-M2 SP2-M3
SP2-D1 SP2-D2 SP2-D3
etc for each spring                 %i need to plot row 1vs2,3vs4,5vs6,etc