Is There an Inequality Between L1 and L2 Norms?

In summary, the conversation discusses the inequality \|x\|_2\le\|x\|_1\le\sqrt{n}\|x\|_2, where |x|1 is the l1 norm and |x|2 is the l2 norm. The conversation includes attempts at solving the inequality and suggestions involving squaring both sides and using Cauchy Schwarz.
  • #1
roho
5
0

Homework Statement


[tex]\|x\|_2\le\|x\|_1\le\sqrt{n}\|x\|_2[/tex]
where |x|1 is the l1 norm and |x|2 is the l2 norm

Homework Equations


See above

The Attempt at a Solution


I have [tex]\|\mathbf{x}\|_1 := \sum_{i=1}^{n} |x_i|[/tex]
and [tex]\|x\|_2 = \left(\sum_{i\in\mathbb N}|x_i|^2\right)^{\frac12}[/tex]
I have tried to expand out the x 2 norm but i can't seem to figure out how to prove the inequality. Any suggestions?
 
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  • #2
for the first part of the inequality, you could try squaring both sides
 
  • #3
Yea that works for the first part. Thanks for the reply.

Any idea on the second part (square root of n)?

I am thinking it may have to do with the projection vector (such as (1,1,1,1,1,1)) in a scalar product or something like.
 
  • #4
your idea should work with for the 2nd one with the use of Cauchy Schwarz
 

Related to Is There an Inequality Between L1 and L2 Norms?

1. What is the difference between L1 and L2 norm inequality?

The L1 and L2 norms are both measures of distance or magnitude in a vector space. The L1 norm, also known as the Manhattan norm, calculates the absolute difference between the values of each element in a vector. The L2 norm, also known as the Euclidean norm, calculates the square root of the sum of the squared values of each element in a vector. Inequality between the two norms refers to the comparison of their values, where L1 norm is typically smaller than L2 norm.

2. How are L1 and L2 norm inequalities used in data analysis?

L1 and L2 norm inequalities are commonly used in data analysis to measure the error or distance between two data sets. This allows for the comparison of different models or predictions in order to determine which one is more accurate. The L1 norm is often used for sparse data sets, while the L2 norm is used for continuous data sets.

3. Can L1 and L2 norm inequalities be applied to non-numerical data?

Yes, L1 and L2 norm inequalities can be applied to non-numerical data, such as text or categorical data. In these cases, the data must be converted into numerical values in order to calculate the norms. For example, text data can be converted into numerical values using techniques like bag of words or word embeddings.

4. How do L1 and L2 norm inequalities relate to machine learning algorithms?

L1 and L2 norm inequalities are commonly used in machine learning algorithms as a form of regularization. Regularization helps to prevent overfitting and improve the generalization of the model by adding a penalty term based on the norm of the model's parameters. L1 norm is often used for feature selection, while L2 norm is used for weight decay.

5. Are there any other types of norm inequalities besides L1 and L2?

Yes, there are other types of norm inequalities, such as Lp norm and max norm. Lp norm is a generalization of L1 and L2 norms and is calculated by taking the pth root of the sum of the pth powers of each element in a vector. Max norm, also known as L∞ norm, is the maximum absolute value of all elements in a vector. These norms are also commonly used in data analysis and machine learning.

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