There are a number of situations where it is useful to set matplotlib.rcParams['text.usetex'] = True. In this case, special LaTeX characters such as % have to be escaped in places like axis labels. Is there a function built in to matplotlib for escaping LaTeX symbols?
There is a hint of such a thing in the docs here and here, but no clear mention.
The specific problem I am trying to tackle is using a matplotlib.ticker.PercentFormatter, where a custom symbol (symbol=r'\%') must be used if rcParams['text.usetex'] is true. I am trying to add a PR that will escape the percent symbol in PercentFormatter if rcParams['text.usetex'] is enabled, but it does not make sense to only check for the percent symbol in that case, so I would like to escape the entire symbol string.
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I'm trying to make a title for a plot, but the title includes a variable, which I'm inserting using an f-string, but it also includes a Latex expression. I either get an error that f-string expressions do not take \ character, or else it's trying to read what's inside the equation as variables and complaining that it's not defined.
The code I'm trying looks something like this:
test = 'TEST'
plt.plot(1234,5678)
plt.title(f"This is a {test}: ${\sqrt{b/a}}$")
plt.show()
This code will give me the error: "f-string expression part cannot include a backslash", and when I try this (note the extra brackets):
test = 'TEST'
plt.plot(1234,5678)
plt.title(f"This is a {test}: ${{\sqrt{b/a}}}$")
plt.show()
I get this error: "name 'b' is not defined"
I want it to just show a square root of b/a, where b and a are just the letters, not variables, so that it looks something like the plot below:
but I can't seem to make it work with an f-string variable also in the title.
It has to be done like this:
plt.title(f"This is a {test}: ${{\sqrt{{b/a}}}}$")
Since you need to use the { and } characters, they need to be doubled up so that they are interpreted as literal characters. This will prevent it from interpreting the contents between the brackets as a Python expression. Thus, it will no longer complain about the backslash or undefined variables.
Alternatively, it can be put in a separate string to avoid doubling up the brackets. This is more readable in my opinion.
tex = "${\sqrt{b/a}}$"
plt.title(f"This is a {test}: {tex}")
There are times when you need to input modified variables with diacritical marks, or superscripts.
Seems like declare_index_properties allows doing it at the stage of display print.
But it is neither simple, nor very useful in formulas.
is there a simple way of adding hats, umlauts, and ', "strokes on top of a symbol, making it distinguishable from the symbol without such mark both to interpreter and to human eye?
Maxima doesn't have a notion of declaring a symbol to have diacritical marks or other combining marks on it. However, Maxima allows Unicode characters in symbol names if the underlying Lisp implementation allows Unicode; almost all of them allow Unicode. GCL is the only Lisp implementation, so far as I know, which doesn't handle Unicode correctly.
WxMaxima appears to allow Unicode characters to be input. At least, it worked that way when I tried some examples. Command-line Maxima allows Unicode if the terminal it is running in allows Unicode.
I think any Unicode character should be OK in a string. For symbols, any character which passes ALPHA-CHAR-P (a build-in Lisp function) can be part of a symbol name. Also, any character which is declared to be alphabetic (via declare("x", alphabetic) where x is the character in question) can be part of a symbol name.
I think wxMaxima has some capability to allow the user to select characters with diacritical marks from a menu; I haven't tried it. When I want to use Unicode characters, I end up just pasting them from a web page or something. I have used https://www.w3.org/2001/06/utf-8-test/UTF-8-demo.html as a source of characters in the past.
In julia you can write subscripts by \_ for variable names. I was wondering if there is anything similar for writing fractions in variable names. Something like \frac{}{} in LaTeX. I understand this may be harder as it takes two arguments. If there is none, I will use /. But in this case I would like to use some enclosures to make clear what is being differentiated. I assume () is not usable? [] or {} would be ok?
The subscripts or other non-latin names you see in Julia code are just normal unicodes the same as "regular" names. the LaTeX commands are only a function of Julia REPL to remember and input them.
As for unicode, in principle you can represent some simple fractions like ⁽²⁺ⁱ⁾⁄₍ₛ₊ₜ₎, using the ⁄ (U+2044 Fraction slash) symbol and subscripts and superscripts. The rendering depends on your font, but do not expect a verticle layout in any current fonts.
However, Julia recognizes ⁄ (U+2044 Fraction slash, not the / in your keyboard) as "invalid character" when used along during parsing. The same applies to \not, which can only be used in conjunction with some operators, so it's not an option too.
As for the brackets and the normal /, they are operators and are parsed differently. However, there is an (ugly) way to circumvent this: you can use macros to bypass the parsing and use strings as variable names. For example:
julia> macro n_str(name)
esc(Symbol(name))
end
#n_str (macro with 1 method)
julia> n"∂(2x + 3)/∂x" = 2
2
julia> 2n"∂(2x + 3)/∂x"
4
My program makes calculations on physics vectors and it allows copy/pasting from websites and then tries to parse them into the x, y, and z components automatically. I've come across one website (http://mathinsight.org/cross_product_examples) that has (3,−3,1). While that looks normal, that minus is actually not recognized by VB. Visually, it is longer than the normal minus (− and -), but return the same Unicode of 45. This picture shows the Unicode for every character (I added a minus in front of the first 3 for comparison) in the Textbox. Also, from this website, I had to use Ctrl+c because right clicking shows that this is not simple HTML.
One is valid (the first), but the second gives VB fits as shown below. Either it won't compile (shown by the blue line below) or a simple assignment (the second one) wrecks havok on my form.
I have tried using
vectorString.Replace("–", "-")
and pasting in the longer dash for the target string and a normal keystroke dash as the replacement, but nothing happens. I'm guessing that since they both have the same Unicode.
Is there some way to convert the longer, invalid dash into the one recognized by VB? I tried using dash symbol that Word likes to replace the minus sign with and it comes up as Unicode 150. So, apparently there are at least three different kinds of dashes. Any thoughts?
The character from Math Insight is U+2212, minus sign. The character you tried using in your Replace call is U+2013, en dash. That's why your replace didn't work.
Beyond the standard ASCII hyphen (-, U+0045), there are two common dashes: the en dash (–, U+2013) and the em dash (—, U+2014). There is also a figure dash (‒, U+2012), but it is not as common.
I'm trying to make a console-based program that makes use of ANSI escape codes with GNU Smalltalk. I can't seem to figure out how to go about printing a string object formatted with ANSI escape codes. I've tried the following.
'\x1b[31mHi' displayNl
This prints the entire string, including the escape code, without any formatting. I would have expected this to print "Hi" in red (and then everything else in the console after that, as I didn't reset the color.)
After googling a bit, I was able to find a couple issues on mailing lists where people were trying to produce things like newlines using "\n". Most of the answers were using the Transcript object's cr method, but I didn't find anything about colors in the textCollector class.
It looks like it shouldn't be all that hard to create my own module in C to achieve this functionality, but I'd like to know if there's a better way first.
I'm aware of the ncurses bindings, but I'm not sure that'd be practical for just making certain pieces of text in the program colored. So, is there a standard way of outputting colored text to the terminal in GNU Smalltalk using ANSI escape sequences?
Ended up getting an answer on the GNU Smalltalk mailing list. Looks like you can use an interpolation operator to achieve this.
For example ('%1[31mHi' % #($<16r1B>)) displayNl. would change the color to red, and ('%1[34mHi' % #($<16r1B>)) displayNl. would change the color to blue.
Basically, the % operator looks for a sequences that look like "%(number)" and replaces them with the objects in the array to the right of the operator. In our case, the array has one item, which is the ascii escape character in hexadecimal. So the "%1" in "%1[31mHi' is being replaced with the escape character, and then printed.
(This answer was stolen almost verbatim from Paolo on the GNU Smalltalk mailing list.)