How to define a text variable using an older text variable?

Question

Martín Pérez Estébanez 2022-3-24

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https://ww2.mathworks.cn/matlabcentral/answers/1679439-how-to-define-a-text-variable-using-an-older-text-variable

评论： Stephen23 2022-3-24

Hi, I have a bunch of csv files that I would like to import into my MATLAB. The files share a common part of the name, but contains some variations. To make it easy, I would like to make a set of names for the variables that I want to import, but I am not sure how to do it.

I will give you an example. Giving the following variable "n", how can I generate a set of "mi" string variables based in "n" like in the example?

n="batch1"

m1="batch1_1"

m2="batch1_2"

.

mi="batch1_i"

Thank you very much!

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Stephen23 2022-3-24

编辑：Stephen23 2022-3-24

"To make it easy, I would like to make a set of names for the variables that I want to import,..."

It is the opposite of easy.

Naming the variables dynamically would be slow, complex, inefficient, obfsucated, liable to bugs, and difficult to debug:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

"...but I am not sure how to do it."

Don't do it.

"Giving the following variable "n", how can I generate a set of "mi" string variables based in "n" like in the example"

MATLAB is designed to use arrays. You should use arrays, with indexing. Indexing is neat, simple, and very efficient (unlike what you are trying to do). Using indexing is what the MATLAB documentation shows here:

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

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Answer 1

Voss 2022-3-24

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在 MATLAB Online 中打开

This will create a set of numbered variable names based on n. You can use the resulting m as your list of variable names.

(There are two different approaches depending on if n is a string or a character vector - it's a string in the question, like you said.)

n = "batch1"; % string n
m = string(sprintfc(n+"_%d",1:10).') % string array m
m = 10×1 string array
    "batch1_1"
    "batch1_2"
    "batch1_3"
    "batch1_4"
    "batch1_5"
    "batch1_6"
    "batch1_7"
    "batch1_8"
    "batch1_9"
    "batch1_10"
n = 'batch1'; % in case you had a character vector n
m = sprintfc([n '_%d'],1:10).' % cell array of character vectors m
m = 10×1 cell array
    {'batch1_1' }
    {'batch1_2' }
    {'batch1_3' }
    {'batch1_4' }
    {'batch1_5' }
    {'batch1_6' }
    {'batch1_7' }
    {'batch1_8' }
    {'batch1_9' }
    {'batch1_10'}

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Voss 2022-3-24

编辑：Voss 2022-3-24

@Stephen I was using the term "variable names" as I imagine the OP intended it - to refer to column headers in csv files (or parts of the files' names), not variables in the MATLAB workspace.

Stephen23 2022-3-24

@_: you may be right. Why why why why did TMW pick the same terminology?

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Answer 2

Arif Hoq 2022-3-24

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https://ww2.mathworks.cn/matlabcentral/answers/1679439-how-to-define-a-text-variable-using-an-older-text-variable#answer_925974

在 MATLAB Online 中打开

x=1:10;
T = compose("batch1_%d.csv",x(:))
T = 10×1 string array
    "batch1_1.csv"
    "batch1_2.csv"
    "batch1_3.csv"
    "batch1_4.csv"
    "batch1_5.csv"
    "batch1_6.csv"
    "batch1_7.csv"
    "batch1_8.csv"
    "batch1_9.csv"
    "batch1_10.csv"