## Difference and best practices, global variable or native react context

I am new to React Native and would like to objectively understand:

What is the difference between using `global.variavel = foo;` or create a context API?

& # 39; React recently implemented Context Api in its library replacing Redux & # 39;

In a situation like: Pass data taken from a page (component) And store to be used in another area on another page (component).

Which one should I use?
why
Are they the same things?

I didn't find much related article explaining "Simple and objective" and I have this doubt that for me right now it is very important for a project!

## javascript – how to define the value of a select using a php variable?

I have the following select of the months of the year and an input where it shows me the selected option, I want the option of the current month selected by default When I start the page, for this I have a php variable where I define what month I am in.
I have searched and cannot find a solution. Is there any way to do it?

``````var mostrarValor = function(x)
{
document.getElementById('pseudonimo').value = x;
}``````
``````

Enero
Febrero
Marzo
Abril
Mayo
Junio
Julio
Agosto
Septiembre
Octubre
Noviembre
Diciembre

``````

## linear algebra: normalization of discrete data against a second variable

I have a recorded flow and temperature data inside a tube for a couple of hours. (See attached photo, please. The horizontal axis should represent time, but here I replace it with counters). Before starting the recording, I expected to have a constant amount of flow over time. When the recording ends, I noticed that the flow has varied over time in some way with the temperature. Now I suspect that changes in temperature cause variations in the flow. Therefore, I want to mathematically eliminate the effects of the temperature change of the flow measurement in some way that I have no idea how. Or, if possible, find some correction factors that compensate for the flow measured by temperature variations.
I'm sorry if my question is too basic, I've been away from math for 15 years.
Thanks in advance.

Variations of flow and temperature

## How can I use a variable within a loop that has been called using the locals () function in python

The following code is a time series, where I save the result in dictionaries with different names according to the loop:

``````from glob import glob
filenames = glob('*.csv')
dataframes = (pd.read_csv(f, parse_dates=('Fecha_Hora'),  index_col='Fecha_Hora') for f in filenames)

for i in range(len(dataframes)):
locals()('d1_'+str(i)) = {'media_diaria_dataframes_var1_'+str(i):dataframes(i).set_index(dataframes(i).index).groupby(pd.Grouper(freq='D'))('var1').mean(),'media_diaria_dataframes_var2_'+str(i):dataframes(i).set_index(dataframes(i).index).groupby(pd.Grouper(freq='D'))('var2').mean()}
``````

and I want to use each dictionary as a dataframe but I don't know how to use the names that are saved with the locals () function within the same loop.

Any ideas.

Thanks in advance.

## CSS variables: input: focus does not set variable

I have this simple example:

``````

:root {
--textbox-box-shadow: none;
}
.example3 {
display: block;
border: 1px solid red;
padding: 10px;
box-shadow: var(--textbox-box-shadow);
}

.example3 input:focus {
--textbox-box-shadow: inset 0 1px 1px rgba(0,0,0,.075), 0 0 6px red;
}

Enter your name :

``````

I'm trying to make the & # 39; div & # 39; Shine when the input element inside it is focused.

The code does not work and I cannot understand why.

By the way, when the variable is given an initial value of
`inset 0 1px 1px rgba(0,0,0,.075), 0 0 6px red;`
instead of "none", the div lights up in red.

How can i fix it ?

The example can be found here.

## python: how to use a value in a variable as part of a string?

I decide to learn Python, and I have a basic question, how can I get the value of the variable and use it as part of a command?
Example:

``````count = 1
tn.write(b'ip address 10.0.0.count 0n')
``````

I would like to use the value 1 of my account as the last digit of my IP address that I will send to a router …
Thank you

## Using the Apache server variable within the section

I have the following configuration within the virtual host (I have omitted some variables for clarity)

``````
DocumentRoot my_website

header set x-robots-tag "noindex"

``````

This sets the `x-robots-tag` header. To confirm that it works, I do `curl -I https://my_site.com` that returns:

``````x-robots-tag: noindex
``````

The problem is that if I change the line:

``````
``````

to

``````
``````

Now him `curl` the command does not return the `x-robots-tag`. Why does the server variable not work inside? ?

To find the problem, I tried to get the value of `%{DOCUMENT_ROOT}` I like this:

``````
header set x-robots-tag "%{DOCUMENT_ROOT}e"

``````

but now `curl` Returns:

``````x-robots-tag: (null)
``````

## adjustment: combine adjusted parameters to make a variable and tell me the error

I have adjusted my data set to a form function: $$a * cos (2 pi t) + b * sin (2 pi t) + c * cos (4 pi t) + d * sin (4 pi t) + e$$ With a non-linear model setting. The parameters $$a, b, c, d, e$$ they have errors that Mathematica would give me, from the covariance matrix. I want to calculate the phase that is given by $$arctan (-b / a)$$, and I want Mathematica to tell me the error in the phase. it's possible?

## stochastic processes: variance of a random variable obtained from a linear transformation

Edit: I needed to review this question as suggested.

Suppose there are $$N$$ Realizations of the Gaussian process denoted as vectors $$mathbf {z} _ {j} in mathbb {R} ^ {n}$$ for $$j = 1, ldots, N$$. Leave $$and$$ be a random variable such that $$y = sum_ {j = 1} ^ {N} ( mathbf {B} mathbf {z} _ {j}) (i)$$
where $$mathbf {B}$$ It is a unitary matrix. What is the variance of $$y2$$?

Explanation: Boldface represents the vector or matrix. $$( mathbf {B} mathbf {x}) (i)$$ represents the $$i$$-th vector entry $$mathbf {B} mathbf {x}$$.

## javascript – Concatenate a URL with VUE variable data

I have a question for many, it will be something very simple but I am getting gray this topic ..

I have a web application, written in vue using template jade this brings some variables and I need to concatenate a url with that variable data ..

``````grd-row
.grd-row-col-3-6 Exchange:
.grd-row-col-3-6 {{ data.watch.exchange }}
.grd-row
.grd-row-col-3-6 Currency:
.grd-row-col-3-6 {{ data.watch.currency }}
.grd-row
.grd-row-col-3-6 Asset:
.grd-row-col-3-6 {{ data.watch.asset }}
``````

Now suppose the variables are composed like this:
data.watch.currency = BTC, data.watch.asset = BNB, data.watch.exchange = binance

``````em You can track this Pair
a(href='https://www.binance.com/en/trade/pro/' + data.watch.currency + "_" + data.watch.asset, target='_blank')   on  {{ data.watch.exchange }}
``````

what I hope is that the url concatenates me like this and you generate this URL to me https://www.binance.com/en/trade/pro/BTC_BNB