Is it possible to create a function for display variables with their names on figures?

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Mr M.
Mr M. 2015-4-14
评论： Thorsten 2015-4-15
For example I have variables: N = 1000; x = 10.5; y = -2.5; dt = 0.001; type = 'nonlinear' etc.
And I want a function with the following syntax:
display_on the_plot(N,dt,x,y,type) or display_on the_plot('N','dt','x','y','type')
which print the following text on the current plot:
'N = 1000, dt = 0.001, x = 10.5, y = -2.5, type = nonlinear'

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回答（4 个）

Guillaume
Guillaume 2015-4-14
Actually Thorsten, "That's impossible. If you pass the name, like display_in_plot('N', 'x'), the values of N and x are unknown inside the function. Likewise, the names are unknown if you pass the values, like in display_in_plot(N, x)."
Either way is actually possible and supported in matlab (even if it feels like a hack).
Passing the variable values, use inputname:
function str = generate_varstring_fromvalue(varargin)
%calling syntax:
%generate_varstring_fromvalue(N, dt, x, y, type)
for vidx = 1:nargin
vname = inputname(vidx);
vvalue = num2str(varargin{vidx});
str{vidx} = sprintf('%s = %s', vname, vvalue);
end
str = strjoin(str, ', ');
end
Passing the variable names, use evalin:
function str = generate_varstring_fromname(varargin)
%calling syntax:
%generate_varstring_fromname('N', 'dt', 'x', 'y', 'type')
for vidx = 1:nargin
vname = varargin{vidx};
vvalue = num2str(evalin('caller', vname));
str{vidx} = sprintf('%s = %s', vname, vvalue);
end
str = strjoin(str, ', ');
end
Thorsten
Thorsten 2015-4-14
text(x, y, ['N = ' int2str(N) ', dt = ' num2str(dt) ', x = ' num2str(x) ', type = ' type])
pfb
pfb 2015-4-14
where do you want that printed?
Have you considered using the builtin function "title"?
ttl = sprintf('N = %d, dt = %1.4f, x = %1.4f, y = %1.4f, type = %s',N,dt,x,y,type);
title(ttl);
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Guillaume
Guillaume 2015-4-14
@Mr M., then see my answer. Either of the two functions I've written will generate the text string for your plot. You then just need to insert the string in the plot with text.

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Thorsten
Thorsten 2015-4-14
编辑：Thorsten 2015-4-14
That's impossible. If you pass the name, like display_in_plot('N', 'x'), the values of N and x are unknown inside the function. Likewise, the names are unknown if you pass the values, like in display_in_plot(N, x).
An awful way to do it would be to declare all variables that the function has to process at any time as global outside the function, pass their names, as in the first example, declare them as global in the function using eval and then generate the string using another eval. You probably need another
eval(['x = whos' name ');'])
to determine the class of the variable (string or double or ...) to decide how to convert it to a string.
Overall, it seems that you can do something like you want, but it involves a lot of global declarations and eval, which is not a good programming style.
A better way would be to pass parameter, value pairs to the function, such as
display_in_plot('N', N, 'x', x, 'type', type)
if you insist on doing it with a function instead of using assembling the string w/o a function.

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