Matlab Subs (2024)

FAQs

What does the subs function do in MATLAB? ›

subs replaces the values in the symbolic function formula, but it does not replace input arguments of the function. Replace the arguments of a symbolic function explicitly.

subs (Symbolic Math Toolbox) Symbolic substitution in a symbolic expression or matrix. subs(S) replaces all occurrences of variables in the symbolic expression S with values obtained from the calling function, or the MATLAB workspace. subs(S,old,new) replaces old with new in the symbolic expression S .

syms lists the names of all symbolic scalar variables, functions, matrix variables, matrix functions, and arrays in the MATLAB workspace. S = syms returns a cell array of the names of all symbolic scalar variables, functions, matrix variables, matrix functions, and arrays.

S = simplify( expr ) performs algebraic simplification of expr . If expr is a symbolic vector or matrix, this function simplifies each element of expr . S = simplify( expr , Name,Value ) performs algebraic simplification of expr using additional options specified by one or more Name,Value pair arguments.

Additional functions within the file are called local functions, and they can occur in any order after the main function. Local functions are only visible to other functions in the same file. They are equivalent to subroutines in other programming languages, and are sometimes called subfunctions.

To substitute a number into an algebraic expression, all you need to do is re-write the expression in exactly the same way, except replacing the variable (letter) with the number. It always makes it clearer to put the number in brackets too. Then you can simplify your new expression and you have your answer!

isequal(A,B) checks if A and B are the same size and their contents are equal (from a coding perspective). To check whether the condition A == B is always mathematically true for all values of variables in A and B , use isAlways(A == B) .

newStr = strrep( str , old , new ) replaces all occurrences of old in str with new . If any input argument is a nonscalar string array or cell array of character vectors, then the other input arguments must have compatible sizes.

You can use the syms command to clear variables of definitions that you previously assigned to them in your MATLAB session. syms clears the assumptions of the variables. These assumptions (which can be real, integer, rational, and positive) are stored separately from the symbolic object.

What is == in MATLAB? ›

== is the element-wise equality comparison operator. https://www.mathworks.com/help/matlab/matlab_prog/matlab-operators-and-special-characters.html? s_tid=doc_ta. A = B; % Assigns the value of B to the variable A. A == B % The result of comparing the elements of A to B for equality.

pretty( X ) prints X in a plain-text format that resembles typeset mathematics. For true typeset rendering, use Live Scripts instead. See What Is a Live Script or Function?

isolate( eqn , expr ) rearranges the equation eqn so that the expression expr appears on the left side. The result is similar to solving eqn for expr . If isolate cannot isolate expr , it moves all terms containing expr to the left side. The output of isolate lets you eliminate expr from eqn by using subs .

z = complex( a , b ) creates a complex output, z , from two real inputs, such that z = a + bi . z = complex( x ) returns the complex equivalent of x , such that isreal(z) returns logical 0 ( false ).

lcm (MATLAB Function Reference) L = lcm(A,B) returns the least common multiple of corresponding elements of arrays A and B . Inputs A and B must contain positive integer elements and must be the same size (or either can be scalar).

Primary and Sub-Functions

Primary functions can be called from outside of the file that defines them, either from command line or from other functions, but sub-functions cannot be called from command line or other functions, outside the function file.

The subroutine is able to call a function, f(x,y), specified by you. Here a subroutine is defined that will approximate a D.E. using Euler's method. If you do not know how to create a file see our tutorial on executable files. In this example, we will approximate the D.E. y'=1/y.

rank (MATLAB Function Reference) The rank function provides an estimate of the number of linearly independent rows or columns of a matrix. k = rank(A) returns the number of singular values of A that are larger than the default tolerance, max(size(A)) * norm(A) * eps .

The subs() function in SymPy replaces all occurrences of first parameter with second. This function is useful if we want to evaluate a certain expression. For example, we want to calculate values of following expression by substituting a with 5.