How to use the constant e in MATLAB?

So the question is given x =0.2 calculate (x^2) *e^4. I know for pi you just type pi which is just pi in the command. But how do I type e in the command window. Also how to use exponents? Do you just go (x^2) ? Do I need those brackets?

[Kenneth Gabriel]

sweet thx

[James Tursa]

If Star's answer met your needs, please formally Accept it.

[Xingyu Xia]

exp()=e^

[Abdalla]

x1 = 𝑒𝑗8𝜋/7

[Voss]

x1 = exp(1j*8*pi/7)

x1 = -0.9010 - 0.4339i

[Jeeimy]

Y=e^(1.2*t)

[DGM]

Use exp(). It's the same answer that's already been demonstrated several times on this page.

[Neliswa]

when i am using this normal e the code does not work mos, what should i do?

[Stephen23]

"when i am using this normal e the code does not work mos, what should i do?"

https://www.mathworks.com/matlabcentral/answers/302984-how-to-use-the-constant-e#answer_234664

Answer 1

[Star Strider]

Use the exponential function exp(y) to compute e^y. For example: 

x = 0.2;  
Result = (x^2)*exp(4)  

Result = 

     2.1839 

[Cai Walsh]

say i needed Vout = VS (1 − e^-T/RC) , how would i write this as ive tried exp(-T/R*C) but wouldt work as theres a negative

[Steven Lord]

T = 2;
R = 5;
C = 7;
y = exp(-T/R*C)

y = 0.0608

z = exp(-14/5)

z = 0.0608

Or did you want to divide by the product of R and C?

w = exp(-T/(R*C))

w = 0.9445

q = exp(-2/35)

q = 0.9445

[Andrei]

For more details, see exp documentation page: exp - Exponential - MATLAB

Answer 2

[Harsh]

e=exp

then use bracket

i.e. e^5=exp(5) in matlab

Answer 3

[John D'Errico]

There are significant issues in this. Some (@Harsh, for example) have suggested creating a variable named e. And while this can work, it also has problems.

First, exp is vectorized. That is, if you define e as a variable, beware if the exponent is a vector or array. You WILL need to use the .^ operator. It will fail if you do not.

e = exp(1);
x = 1:5;
e.^x

ans = 1×5

2.7183 7.3891 20.0855 54.5982 148.4132

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e^x

Error using ^ (line 29)
Incorrect dimensions for raising a matrix to a power. Check that the matrix is square and the power is a scalar. To operate on each element of the matrix individually, use POWER (.^) for elementwise power.

Next, can you raise a negative value? That is, suppose you have the expression e^-x^2, where this is a gaussian like thing? So you need to compute -x^2, then raise e to that power.

>> x = 2;
>> e^-x^2
ans =
0.018316
>> e^(-x^2)
ans =
0.018316

As you can see, both yield the same result due to the order of operations in MATLAB as long as you use the vectorized operator when vectrs or arrays are involved, but using parens is FAR FAR safer, if you have even the slightest uncertainty about how such an expression will be evaluated.

The biggest issue is with time. exp is considerably faster to evaluate, if the arrays are at all large.

>> x = randn(1,1e8);
>> timeit(@() e.^x)
ans =
0.22558
>> timeit(@() exp(x))
ans =
0.056586

The difference is essentially 4 to 1 faster for exp.