Plotting a graph for step length

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Kedar 2014-10-8

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https://ww2.mathworks.cn/matlabcentral/answers/157907-plotting-a-graph-for-step-length

评论： Star Strider 2014-12-5

Hi. I have a data set that I need to plot against time. X=time. Y in this case is a step length recorded as '1' for right and '1' for left over the entire trial duration.

I need to plot this step length (left '1' to right '1' connecting line) over time.

I am not a Matlab user so need a guidance with this.

Thank you.

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Star Strider 2014-10-11

Plotting the steps (R & L) as functions of time is easy.

How do you define step length?

Kedar 2014-10-11

编辑：Kedar 2014-10-11

I wouldn't say it is easy. This is possibly my first time to use Matlab. Left step length is defined as distance covered from left heel strike to right heel strike and similarly right side.

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采纳的回答

Star Strider 2014-10-12

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/157907-plotting-a-graph-for-step-length#answer_154834

编辑：Star Strider 2014-10-12

在 MATLAB Online 中打开

ImportAvatar0007.m

This is a bit much for an introduction to MATLAB.

The code begins by using the find function to determine the indices where ‘SoundLeft’ and ‘SoundRight’ are equal to 1, in ‘LSteps’ and ‘RSteps’ respectively. It then uses the index vectors to determine the times (denoted by the ‘Time’ vector) that the respective steps occur, in ‘LStepT’ and ‘RStepT’ respectively. Since you wanted the time differences between heel-strike for the left and right foot separately, all I then needed to do was the calculate the time differences between the successive heel strikes, and for that I used the diff function for each foot, in ‘LStepL’ and ‘RStepL’. Those are one element shorter than the corresponding ‘LStepT’ and ‘RStepT’, necessitating the (1:end-1) subscripts in the plot call. [The EDIT is this explanation, since you mentioned this was your first time using MATLAB.]

See if this does what you want:

[Time,Avatar_On,Sound_On,Sequenceindex,Condition,Treadmillpos,Treadmilltime,Treadmillspeed,SoundLeft,SoundRight,Avatar1pos,Avatar2pos,Avatar3pos,Action,AvatarSpeed,time,timespeed] = ImportAvatar0007('Avatar0007.txt',2, 33118);
LSteps = find(SoundLeft == 1);
RSteps = find(SoundRight == 1); 
LStepT = Time(LSteps);
LStepL = diff(LStepT);
RStepT = Time(RSteps);
RStepL = diff(RStepT);
figure(1)
plot(LStepT(1:end-1), LStepL)
hold on
plot(RStepT(1:end-1), RStepL)
hold off
grid
xlabel('Time')
ylabel('Step Length (s)')
legend('Left', 'Right', 'Location','NE')

The code for the function MATLAB created to read your file (using textscan) is attached for you to use. My code requires it because I refer to the variables it creates.

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Star Strider 2014-10-12

My pleasure!

I doubt if med school will teach you anything at all about MATLAB. I learned FORTRAN as an undergraduate (chemistry major), and had nothing at all about technology in med school. I went back to get a M.S. in Biomedical Engineering after I earned my M.D., completed my residency, and got my Board Certification in Internal Medicine, in order to correct for my deficient knowledge of technology, mathematics, and statistics. In the U.S., the M.D. is not a research degree, and I suspect the same is true in Canada, so it alone will not give you a sufficiently robust background to do research. Your studies will be entirely clinical. (That is actually necessary, because of the volume and complexity of what you will be studying.) If you want to remain involved in research, I would advise you to take one of two paths: do essentially as I did, in the same order (possibly going for a Ph.D. rather than stopping with a M.S.), or do an M.D.-Ph.D. program (something I considered). You will need specialty Board Certification, so be sure to accomplish that. This is not easy, but it is definitely worthwhile.

I look forward to hearing from you.

Kedar 2014-10-16

编辑：Kedar 2014-10-16

Ok. Apologies for this confusion and error. I have given you only the columns that are necessary now. They are step time (time taken to make left step and similarly for right step), step distance (distance covered by that step in the given time) and absolute start time (time for the whole trial). These three columns are for left and right leg. These parameters are derived from motion capture system using other Matlab scripts. The recording frequency for this motion capture system is 120Hz and all values are in mm for distance and seconds for time.

Like previously we plotted step length for avatar from the other file, I want to plot the step length (of the participant) from this attached file over time (x-axis). However they have different frequency of recording. I guess I will have to put in an interpolation (intrep1) function to have same no. of recording points over that time duration and than plot these 2 step length (avatar and the participant). Hope it is a bit clear. Sorry about that.

Also regarding 'accept this answer', there is not place to do that. I saw that option in the other to fellows who provided me some guidance on plotting. I am attaching a screenshot, to help us with that.

Thanks a lot.

Star Strider 2014-11-26

That means that ‘info’ doesn’t exist in your workspace.

You need to go through your code to understand the reason. (If you intend to create it in an if block for instance, the if condition may not be met so the block never executes. I’m just guessing here.)

Star Strider 2014-11-28

You need to create ‘info’ and put something in it. (Empty variables can occasionally cause problems.)

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