Why isn't this file loading method working?

Question

Kieran Fung 2021-5-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/830173-why-isn-t-this-file-loading-method-working

评论： DGM 2021-5-14

matlab_help.JPG

I've had success in the past piecing together proper file strings name to call upon the right file name. Here I'm trying to compare saved data sets and plot their data series one at a time, since all data sets share the same variable names.

I figured I could just loop through each file name and plot their respective series independent of one another simply by using the 'hold on' syntax to keep previous data sets since all files of interest I want to compare all have the same variable names. That makes sense right? I would just grab one variable of a data set, plot it and hold on, and rewrite over the variable name for the next data set of interest.

I've attached a code screen shot for reference. The two files/datasets I'm working with right now can be seen in the current folder workspace. Like I've said, I've used this technique in the past but cannot recognize why the data sets are not being loaded.

Any advice would be appreciated!

6 个评论
显示 4更早的评论隐藏 4更早的评论

Kieran Fung 2021-5-14

Hey DGM and Stephen,

I recognized both of your precense in the thread and wanted to ask a followup question after reviewing that link. Although I didn't understand everything that was being discussed, proposed, etc. - WRT the suggestion of:

s = load(...)

To my understanding, this is more helpful for the solver because the outputted 's' will remain constant throughout my loop, even though the actual loading file will not? Why is this beneficial? I'm not fully connecting the dots because the loaded file name will be chaning periodically for 'N' amount of files, even though 'S' will be constant.

Thanks!

- dynamic struct newbie

DGM 2021-5-14

在 MATLAB Online 中打开

Someone can offer a more technically thorough explanation than I can, but if you do something like

load('mybigfilefullofstuff.mat');
y = x*2;
z = mean(y);

Prior to running, or at parse time, how does Matlab know anything about where x came from? It can't know how many other things are going to show up in the workspace until it actually loads the file at run time. It defeats a lot of the guidance that the code tools could give the person writing the code, and it leaves the possibility for all sorts of hard to detect/predict shenanigans to occur. What if one of the variables in that .mat file is called mean?

If you load into a struct:

S = load('mybigfilefullofstuff.mat');
y = S.x*2;
z = mean(y);

Matlab knows ahead of time that y is a function of a thing that came from S which came from load(). It knows that mean() isn't something that came from S.

请先登录，再进行评论。

请先登录，再回答此问题。