How to use dynamic variable in parfor matlab answers. Learn more about dynamic, matrix, output, names image processing toolbox. The dynamic fieldname can return either a character vector or a string scalar. Once they are loaded in the workspace, i want to call name them as variables such as. The maximum length of a variable name is the value that the namelengthmax command returns. Apr 27, 2011 im trying to create a new structure from an already existing structure using dynamic fieldnames no joy however. It is unlikely that you sat and wrote out hundreds of lines of code defining each numbered variable independently, which means that those variables must be imported, input, or created somehow. How to declare variable names from text file names.
Essentially i want to pull all of the active matlab variables from the gpu onto ram, flush the gpu, then put the variables back up. Any character vector that exceeds namelengthmax is truncated in the varname output. View the data type, description, units, and other descriptive statistics for each variable by using summary to summarize the table. Modify units, descriptions, and table variable names matlab. Learn more about dynamic variable names, workspace variables, eval.
When you are a beginner it seems like a cunning and fast way to store information, but actually it is really bad practice to nameaccess variables dynamically. Assume that you want to create a variable in matlab whose name is contingent on factors that are unknown before the program runs. You cannot define variables with the same names as matlab keywords. To the best of my knowledge, it is not possible to dynamically create variable names in matlab. Every tom, dick, and harry uses the arraystyle, which is fine. Once they are loaded in the workspace, i want to call name them as variables such as a1, a2, b1, b2, etc. Hello, i have a similar need deriving from what it seems to be a limitation of the classification learner app. Its possible to test for the existence of fields before access, and its a very handy way to create a stringvalue storage system. You can use the variable name, bloodpressure, or the numeric index of the variable, 6, to index into the cell array of character vectors containing the variable descriptions.
Aug 24, 2017 so im trying to both make and save off a dynamically named variable. The most common alternative is to use simple and efficient indexing. May, 2015 when you are a beginner it seems like a cunning and fast way to store information, but actually it is really bad practice to name your variables dynamically. To learn how to work with symbolic math, see perform symbolic computations. Dynamic structure referencing has its own dangers, but its clearer than dynamic variable creation.
Mathworks is the leading developer of mathematical computing software. A valid matlab variable name is a character vector of letters, digits, and underscores, such that the first character is a letter, and the length of the vector is less than or equal to the value returned by the namelengthmax function. For example, you may want to attach a time or date stamp to the end of a variable name. One of the questions that came out of that discussion was how to get rid of a bunch of eval statements from their code. In matlab, there are 3 basic types of arrays, traditional ones where you index using parentheses, cell arrays where you can address the. My points are no stronger than what the documentation states, which is the dynamically accessing variables is slow, buggy, and complex. Feb29 field names, like variable names, must begin with a letter, can contain letters, digits, or underscore characters, and. User inputs either one of the normal names, or a new struct name code does the same thing regardless but before saving out changes k to the correct struct nameaka the dynamic variable name user can then open the file with the correct name and use it going forward. Construct valid variable name from string matlab genvarname. The maximum length of a variable name is the value that the namelengthmax command returns you cannot define variables with the same names as matlab keywords, such as if or end. Feb 28, 2018 and then you want to use the content of varname as the name of the variable to write to.
The names of these fields are contained in the cell array adds as strings. The gui doesnt accept it and ive only been using matlab for less than a week so i havent learnt how to call the nn function yet in the script. Recently there was an interesting presentation with some really great clutter classification algorithms in a gui. Learn more about dynamic field names, variable names. I am generating a cell array of tables with my program and want to try each of the tables as training features in the classification learner, but the app does not see cell arrays in the workspace. I am generating a cell array of tables with my program and want to try each of the tables as training features in the classification learner, but.
Dynamically name a struct matlab answers matlab central. Mathworks is the leading developer of mathematical computing software for engineers and scientists. Im trying to create a new structure from an already existing structure using dynamic fieldnames no joy however. A way to dynamically create variables in matlab as i say, its messy to do that, and at least you may want to have things stored within a structure, which allows programmatic creation of elements using string variables and dynamic referencing using the paren syntax. How can i create variable names from dynamic field names. We have matlab users come into the mathworks to present their work in matlab from time to time. The preferred method is to store related data in a single array. Now i want to perform a series of operations without having to write the variable names manually for every loop, i just want to have a for loop for my filecounter and execute the commands for cs, ts for every file. Nov 01, 2011 when you are a beginner it seems like a cunning and fast way to store information, but actually it is really bad practice to name your variables dynamically. Generate variable names with a loop matlab answers matlab. Field names that you reference with expressions are called dynamic fieldnames, or sometimes dynamic field names for example, create a field name from the current date. Symbolic numbers are exact representations, unlike floatingpoint numbers. Hiding an index in the name of variables is a bad idea.
How to create variable names matlab answers matlab central. For example, you can specify the field feb29 using either single or, starting in r2017b, double quotes. Ultimately this is a good thing though, because stephens comment is correct that the code will be better if variables are indexed into arrays, rather than large groups of individually named variables. Aug 20, 2008 we have matlab users come into the mathworks to present their work in matlab from time to time. Matlab is case sensitive, so a and a are not the same variable.
Until youre working with arrays and dynamic variables, oh boy. If i do it in eval just need to loop the array of sensor numbers but it is sequential, which means matlab will take ages to process. This page shows how to create symbolic numbers, variables, and expressions. I realize that dynamic named variables are bad and hard to use, however, currently i have 5 different versions of test and its only going to grow. Dynamic variable names for full workspace operations. Movefile with variable file names matlab answers matlab. Sometimes beginners and some selftaught professors think it.
I also tried using eval but i cant seem to get the syntax right. In matlab, there are 3 basic types of arrays, traditional ones where you index using parentheses, cell arrays where you can address the contents. Generate variable names with a loop matlab answers. Create symbolic numbers, variables, and expressions. For example, create a field name from the current date. Dynamic variable names for full workspace operations matlab. In addition, matlab supports dynamic field names field lookups by name, field manipulations, etc. Aug 20, 2008 originally posted on dougs matlab video tutorials blog. Learn more about movefile, variable file names, naming, path. Loading files using their names for variable names. Why variables should not be named dynamically eval. Dynamic field name usage stuarts matlab videos matlab. Use dynamic field references loren on the art of matlab.
Feb 01, 2017 for me this is a perfectly reasonable assumption as i never have unknown variables in my workspace never use load directly into the workspace, avoid assignin, eval, or other dynamic variable names. Creating variable name using sprintf and field of a structure. How to dynamically create variables in matlab stack overflow. A valid variable name starts with a letter, followed by letters, digits, or underscores.
Learn more about eval, dataset, dynamic variable naming, dynamic variable names. Right now i just do it on a variable by variable basis within the code, which works but is also a pain to code and leads to a lot of time. How to create variable names from csv column names. Dire warnings about dynamic variable creation have been added to the answer. Modify units, descriptions, and table variable names. Mathworks is the leading developer of mathematical computing software for engineers. Dynamic in dynamic variable name is the opposite of static as in static variable name, with static variable names being the ones that are hardcoded and unchangeable, and dynamic variable names changing depending on the circumstances. When you are a beginner it seems like a cunning and fast way to store information, but actually it is really bad practice to name your variables dynamically. Aug 21, 2018 how can i create variable names from dynamic. How to assign vectors to each dynamic variable name. Creating variable name using sprintf and field of a. Also another reason is i need to provide a progressive and transparent series of user friendly variables that my professors can understand what they mean without reading every line of my code.
Field names that you reference with expressions are called dynamic fieldnames, or sometimes dynamic field names. Mathworks is the leading developer of mathematical computing. So im trying to both make and save off a dynamically named variable. Dynamically accessing variable names can negatively impact the readability of your code and can cause it to run slower by preventing matlab from optimizing it as well as it could if you used alternate techniques. End goal is to load a variable name that makes sense into the workspace. Valid function names begin with an alphabetic character, and can contain letters, numbers, or underscores.
This is called dynamic field name reference or dot parens notation. Create symbolic numbers, variables, and expressions matlab. All i have done is read a lot of discussions, documentation, and blogs on this topic, and collected them together into one list for anyone who wants to learn how to write efficient matlab code. Forcing metadata into variable names is slow and complex. And for matlab, import data from xlsx, how to get 1st row as variable name, and rest of the column as data for variable name from shai, doesnt work when i change to csvread or textread. If you want to create variables programmatically not a recommended practice, but if you insist, see the previous question. I wish to expand a structure bac with a number of fields from another structure bt.
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