I try to read a text files with 20x20 data into variable C, and attempt to plot a histogram on the left Y-axes, and a ecdf/ksdensity on the right X-axes.
Using textscan, the data is read into a 400x1 array. However, when I tried to call plotyy to plot histogram, the code belows return
Error using plot
Vectors must be the same lengths.
Error in pt (line 11)
axes = plotyy(x,C{1},x,C{1});
I guess it is due to C{1}. But have no clue on how to resolve it. I am new to matlab, would anyone point out the correct way to perform the above operations?
fid = fopen('t1_error.txt','r');
C = textscan(fid, '%.3f');
fclose(fid);
disp(C{1});
x = -1:7; % <-- change to x = length(C{1}); then histogram is plotted.
axes = plotyy(x,C{1},x,C{1});
hold on
hist(axes(1), C{1}, x);
ylim(axes(1),'auto');
set(axes(1),'mode','auto');
hold off
The length of x does not equal the length of C{1}. Try x = 1:length(C{1}) or x = -1:8/length(C{1}):7.
Related
I wish to highlight/mark some parts of a array via plot in MATLAB. After some research (like here) I tried to hold the first plot, find the indexes for highlighting and then a new plot, only with those points. However, those points are being drawn but all shifted to the beginning of the axis:
I'm currently trying using this code:
load consumer; % the main array to plot (157628x10 double) - data on column 9
load errors; % a array containing the error indexes (1x5590 double)
x = 1:size(consumer,1)'; % returns a (157628x1 double)
idx = (ismember(x,errors)); % returns a (157628x1 logical)
fig = plot(consumer(:,9));
hold on, plot(consumer(idx,9),'r.');
hold off
Another thing I would like to do was highlighting the whole section of the graph, like a "patch" on the same sections. Any ideas?
The trouble is that you are only providing the y-axis data to the plot function. By default, this means all data is plotted on the 1:numel(y) x locations of your plot, where y is your y-axis data.
You have 2 options...
Also provide x-axis data. You've already got the array x anyway!
figure; hold on;
plot(x, consumer(:,9));
plot(x(idx), consumer(idx,9), 'r.');
Aside: I'm slightly confused why you create idx. If errors is as you describe it (indexes of the array) then you should just be able to use consumer(errors,9).
Make all data which you don't want to appear equal to NaN. Because of the way you're loading your error indices in, this is less quick and easy. Basically you'd copy consumer(:,9) into a new variable, and index all undesirable points to set them equal to NaN.
This method has the benefit of breaking up discontinuous sections too.
y = consumer(:,9); % copy your y data before changes
idx = ~ismember(x, errors); % get the indices you *don't* want to re-plot
y(idx) = NaN; % Set equal to NaN so they aren't plotted
figure; hold on;
plot(x, consumer(:,9));
plot(x, y, 'r'); % Plot all points, NaNs wont show
Generate a plot showing the graphs of
y=(2*a+1)*exp(-x)-(a+1)*exp(2*x)
in the range x ∈ <-2, 4> for all integer values of a between -3 and 3
I know how to make typical plot for 2 values and set a range on the axes, but how to draw the graph dependent on the parameter a?
To elaborate on Ben Voigt's comment: A more advanced technique would be to replace the for-loop with a call to bsxfun to generate a matrix of evaluations of M(i,j) = f(x(i),a(j)) and call plot with this matrix. Matlab will then use the columns of the matrix and plot each column with individual colors.
%%// Create a function handle of your function
f = #(x,a) (2*a+1)*exp(-x)-(a+1)*exp(2*x);
%%// Plot the data
x = linspace(-2, 4);
as = -3:3;
plot(x, bsxfun(f,x(:),as));
%%// Add a legend
legendTexts = arrayfun(#(a) sprintf('a == %d', a), as, 'uni', 0);
legend(legendTexts, 'Location', 'best');
You could also create the evaluation matrix using ndgrid, which explicitly returns all combinations of the values of x and as. Here you have to pay closer attention on properly vectorizing the code. (We were lucky that the bsxfun approach worked without having to change the original f.)
f = #(x,a) (2*a+1).*exp(-x)-(a+1).*exp(2*x); %// Note the added dots.
[X,As] = ndgrid(x,as);
plot(x, f(X,As))
However for starters, you should get familiar with loops.
You can do it using a simple for loop as follows. You basically loop through each value of a and plot the corresponding y function.
clear
clc
close all
x = -2:4;
%// Define a
a = -3:3;
%// Counter for legend
p = 1;
LegendText = cell(1,numel(a));
figure;
hold on %// Important to keep all the lines on the same plot.
for k = a
CurrColor = rand(1,3);
y= (2*k+1).*exp(-x)-(k+1).*exp(2.*x);
plot(x,y,'Color',CurrColor);
%// Text for legend
LegendText{p} = sprintf('a equals %d',k);
p = p+1;
end
legend(LegendText,'Location','best')
Which gives something like this:
You can customize the graph as you like. Hope that helps get you started!
I have a matrix M of data and a matrix E of errors that I want to plot with errorbar against an independent variable x. I would also like lines between points in the same row. One column in M or E corresponds to one x-value, so this can be accomplished with
errorbar(x, M, E, 'o-')
I am missing some data points and these have the value NaN. As it should errorbar() ignores these, but the line between the points closest two points in the same row (the one resulting from the '-' option) is broken.
I have seen some different solutions that work with vectors as opposed to matrices, involving ~any(isnan(y),1) and L=~(isnan(x)|isnan(y)), but these lead to problems like
Error using errorbar
X, Y and error bars must all be the same length
I can't find a solution for matrices, any ideas?
Because the missing data points are probably not the same for every line I advice to plot in a loop like this (assuming plot data are columns of the matrices):
for i = 1 : size(M, 2)
data = M(:, i);
good = not(isnan(data));
xi = x(good);
data = data(good);
error = E(good, i);
errorbar(xi, data, error, 'o-');
hold on;
end
Hi i am trying to make a simple distribution histogram using some code from stack overflow
however i am unable to get it to work. i know that there are is a simple method for this using statistic toolbox but form a learning point of view i prefer a more explanatory code - can any one help me ?
%%
clear all
load('Mini Project 1.mat')
% Set data to var2
data = var2;
% Set the number of bins
nbins = 0:.8:8;
% Create a histogram plot of data sorted into (nbins) equally spaced bins
n = hist(data,nbins);
% Plot a bar chart with y values at each x value.
% Notice that the length(x) and length(y) have to be same.
bar(nbins,n);
MEAN = mean(data);
STD = sqrt(mean((data - MEAN).^2)); % can also use the simple std(data)
f = ( 1/(STD*sqrt(2*pi)) ) * exp(-0.5*((nbins-MEAN)/STD).^2 );
f = f*sum(nbins)/sum(f);
hold on;
% Plots a 2-D line plot(x,y) with the normal distribution,
% c = color cyan , Width of line = 2
plot (data,f, 'c', 'LineWidth', 2);
xlabel('');
ylabel('Firmness of apples after one month of storage')
title('Histogram compared to normal distribution');
hold of
You are confusing
hist
with
histc
Read up on both.
Also, you are not defining the number of bins, you are defining the bins themselves .
I don't have Matlab at hand now, but try the following:
If you want to compare a normal distribution to the bar plot bar(nbins,n), you should first normalize it:
bar(nbins,n/sum(n))
See if this solves your problem.
If not, try also removing the line f = f*sum(nbins)/sum(f);.
I want to plot a line from one well-defined point to another and then turn it into an image matrix to use a Gaussian filter on it for smoothing. For this I use the functions line and getframe to plot a line and capture the figure window in an image, but getframe is very slow and not very reliable. I noticed that it does not capture anything when the computer is locked and I got an out of memory error after 170 executions.
My questions are:
Is there a substitute to getframe that I can use?
Is there a way to create the image matrix and draw the line directly in it?
Here is a minimal code sample:
figure1=line([30 35] ,[200 60]);
F= getframe;
hsize=40; sigma=20;
h = fspecial('gaussian',hsize,sigma);
filteredImg = imfilter(double(F.cdata), h,256);
imshow(uint8(filteredImg));
[update]
High-Performance Mark's idea with linspace looks very promising, but how do I access the matrix coordinates calculated with linspace? I tried the following code, but it does not work as I think it should. I assume it is a very simple and basic MATLAB thing, but I just can not wrap my head around it:
matrix=zeros(200,60);
diagonal=round([linspace(30,200,numSteps); linspace(35,60,numSteps)]);
matrix(diagonal(1,:), diagonal(2,:))=1;
imshow(matrix);
Here's one example of drawing a line directly into a matrix. First, we'll create a matrix of zeros for an empty image:
mat = zeros(250, 250, 'uint8'); % A 250-by-250 matrix of type uint8
Then, let's say we want to draw a line running from (30, 35) to (200, 60). We'll first compute how many pixels long the line will have to be:
x = [30 200]; % x coordinates (running along matrix columns)
y = [35 60]; % y coordinates (running along matrix rows)
nPoints = max(abs(diff(x)), abs(diff(y)))+1; % Number of points in line
Next, we compute row and column indices for the line pixels using linspace, convert them from subscripted indices to linear indices using sub2ind, then use them to modify mat:
rIndex = round(linspace(y(1), y(2), nPoints)); % Row indices
cIndex = round(linspace(x(1), x(2), nPoints)); % Column indices
index = sub2ind(size(mat), rIndex, cIndex); % Linear indices
mat(index) = 255; % Set the line pixels to the max value of 255 for uint8 types
You can then visualize the line and the filtered version with the following:
subplot(1, 2, 1);
image(mat); % Show original line image
colormap(gray); % Change colormap
title('Line');
subplot(1, 2, 2);
h = fspecial('gaussian', 20, 10); % Create filter
filteredImg = imfilter(mat, h); % Filter image
image(filteredImg); % Show filtered line image
title('Filtered line');
If you have Computer Vision System toolbox there is a ShapeInserter object available. This can be used to draw lines, circles, rectangles and polygons on the image.
mat = zeros(250,250,'uint8');
shapeInserter = vision.ShapeInserter('Shape', 'Lines', 'BorderColor', 'White');
y = step(shapeInserter, mat, int32([30 60 180 210]));
imshow(y);
http://www.mathworks.com/help/vision/ref/vision.shapeinserterclass.html
You can check my answer here. It is robust way to achieve what you are asking for. Advantage of my approach is that it doesn't need additional parameters to control density of the line drawn.
Something like this:
[linspace(30,200,numSteps); linspace(35,60,numSteps)]
Does that work for you ?
Mark