I have a data series and estimated the parameters of the probability density function I wanted. It's a pdf that isn't in the MATLAB "distribution fitting" app and another that is but I modified to be exactly what I wanted.
The problem is when I'm doing the goodness of fit starting to compare the adjusted pdf with the empircal distribution.
I don't know if the y-axis is supposed to be in frequency but I'm doing it all in density.
What I've got:
The red line I'm supposed to have but flipped:
The thing is, in the first graph the normal is nicely enquadrated but the other two distribution are not. First, none was enquadrated but then I normalized the histogram:
histogram(DATAs,'Normalization','pdf')
But as you can see in the second graph the red one is supposed to be along with the histogram while on the first one is completely separated. (It's the same data, the only thing is that in the second one I estimated using the "distribution fitting" app with positive values and I plan to do a flip when passing to the first one).
I'm starting to think that the problem is when plotting the pdf. Do I need to adjust the pdf scale in order to have the second image in the first one?
Supposing that the parameters are correctly estimated. The pdf plot I did like this:
x_DATAs =linspace(minval1,maxval1,10000);
parmhat=[parmhat DATAs(1),parmhatDATAs(2),parmhatDATAs(3)];
y2_ DATAs = sgtpdf(x_DATAs ,parmhat,parmhat DATAs(4),parmhatDATAs(5));
plot(x_ DATAs ,y2_ DATAs , '--g')
I wanted to get something like this:
Related
I had written a code to obtain a threshold pixel value of an image for imaging particles. I have got a plot attached below. I want to choose a point where there is sudden jump in the value. This will be my threshold value. I can manually do this by seeing the point. But I want to do it automatically through code what should I do?
I was thinking of sorting it and finding frequency. Then loop it to compare it with previous value. I want to know what should I choose the minimum difference to between these two values.
What other method should I use?
Here is the Image:
Firstly, what do you mean by "sudden jump"? If I understand well, it means that there is a big difference (descrease) of pixel numbers between two adjecent gray levels. Then you can just right shift the histogram vector, and substract the two vectors, getting a vector containing the differences between two adjacent gray levels. And then, you can choose a threshold. That's all.
I have 8 plots which I want to implement in my Matlab code. These plots originate from several research papers, hence, I need to digitize them first in order to be able to use them.
An example of a plot is shown below:
This is basically a surface plot with three different variables. I know how to digitize a regular plot with just X and Y coordinates. However, how would one digitize a graph like this? I am quite unsure, hence, the question.
Also, If I would be able to obtain the data from this plot. How would you be able to utilize it in your code? Maybe with some interpolation and extrapolation between the given data points?
Any tips regarding this topic are welcome.
Thanks in advance
Here is what I would suggest:
Read the image in Matlab using imread.
Manually find the pixel position of the left bottom corner and the upper right corner
Using these pixels values and the real numerical value, it is simple to determine the x and y value of every pixel. I suggest you use meshgrid.
Knowing that the curves are in black, then remove every non-black pixel from the image, which leaves you only with the curves and the numbers.
Then use the function bwareaopen to remove the small objects (the numbers). Don't forget to invert the image to remove the black instead of the white.
Finally, by using point #3 and the result of point #6, you can manually extract the data of the graph. It won't be easy, but it will be feasible.
You will need the data for the three variables in order to create a plot in Matlab, which you can get either from the previous research or by estimating and interpolating values from the plot. Once you get the data though, there are two functions that you can use to make surface plots, surface and surf, surf is pretty much the same as surface but includes shading.
For interpolation and extrapolation it sounds like you might want to check out 2D interpolation, interp2. The interp2 function can also do extrapolation as well.
You should read the documentation for these functions and then post back with specific problems if you have any.
I am workin on a some sort of System test wherein i have a set of readings in the form of a .mat file.
It has a structure in the .mat file with one field as Measurement. It has several Arrays(e.g air mass flow, velocity, carbon content) which further have fields like time and value.
From these, I Need to plot the velocity and the air mass flow against time. For that i wrote the following command which gave me the corresponding plots:
plot(Measurement.(Measurement.air_mass_flow.time),Measurement.air_mass_flow.value)
plot(Measurement.(Measurement.velocity.time),Measurement.velocity.value)
Now i Need to create a script in matlab wherein i can get both the curves one under the other i.e. on the same page. Can anyone help in the Approach i should procede with ?
ok now i will further extend my question.
I have two fields as velocity and acceleration. I Need to plot it on the same curve with grids on for the comparison. But the y axis for both are different.
the velocity y-axis is: (0:20:120), which should be displayed on the left side and the acceleration y-axis is: (0:2:12) which should be displayed on the right side.
i wrote the following code for this:
plot(Measurement.(Measurement.VehV_v.time),Measurement.VehV_v.value)
grid on
set(gca,'xtick',[0:500:2000])
set(gca,'ytick',[0:20:120])
hold on
plot(Measurement.(Measurement.accel_w.time),Measurement.accel_w.value)
grid on
set(gca,'xtick',[0:500:2000])
set(gca,'ytick',[0:2:12])
Do i Need to write a function for that as i am directly reading the values from the structure.
plotyy() also doesnt seem to work
But the axis are not matching and the graph for acceleration is very small. Could anyone help me out with this ?
I also want to add a Picture of the Graphs here but unfortunately there is some error here. I hope the question is clear without the Picture.
Yes you can use the subplot command, e.g.:
figure
subplot(1,2,1)
plot(Measurement(Measurement.air_mass_flow.time),Measurement.air_mass_flow.value)
subplot(1,2,2)
plot(Measurement.(Measurement.velocity.time),Measurement.velocity.value)
You can use help subplot on Matlab for further details or have a look at this:
https://www.dartmouth.edu/~rc/classes/matlab_graphics/Matlab-subplots.html
I want to create a 5 dimensional plotting in matlab. I have two files in my workspace. one is data(150*4). In this file, I have 150 data and each has 4 features. Since I want to classify them, I have another file called "labels" (150*1) that includes a label for each data in data files. In other words the label are the class of data and I have 3 class: 1,2,3
I want to plot this classification, but i can't...
Naris
You need to think about what kind of plot you want to see. 5 dimensions are difficult to visualize, unless of course, your hyper-dimensional monitor is working. Mine never came back from the repair shop. (That should teach me for sending it out.)
Seriously, 5 dimensional data really can be difficult to visualize. The usual solution is to plot points in a 2-d space (the screen coordinates of a figure, for example. This is what plot essentially does.) Then use various attributes of the points plotted to show the other three dimensions. This is what Chernoff faces do for you. If you have the stats toolbox, then it looks like glyphplot will help you out. Or you can plot in 3-d, then use two attributes to show the other two dimensions.
Another idea is to plot points in 2-d to show two of the dimensions, then use color to indicate the other three dimensions. Thus, the RGB assigned to that marker will be defined by the other three dimensions. Of course, that means you must be able to visualize what the RGB coordinates of a color represent, so you need to understand color as it is represented in an RGB space.
You can use scatter3 to plot your data, using three features of data as dimensions, the fourth as color, and the class as different markers
figure,hold on
markerList = 'o*+';
for iClass = 1:nClasses
classIdx = dataClass==iClass;
scatter3(data(classIdx,1),data(classIdx,2),data(classIdx,3),[],data(classIdx,4),...
'marker',markerList(iClass));
end
When you use color to represent one of the features, I suggest to use a good colormap, such as pmkmp from the Matlab File Exchange instead of the default jet.
Alternatively, you can use e.g. mdscale to transform your higher-dimensional data to 2D for standard plotting.
There's a model called SOM (Self-organizing Maps) which builds a 2-D image of a multidimensional space.
Hi i wanted to generate a single axis graph (dont know if this is called a graph exactly) in matlab something like this
In the above image the numerical values represent time ( 1 till 23) min and the vertical thin black lines represent event A . Some of the vertical black lines have a red circle on top denoting occurrence of an event B along with the event A. Is it possible to generate such a simulated image in matlab ? If so what keywords should i look for. Any suggestions to get me quickly started on generating such a graph/Simulation. (Note: I havent actually used matlab a lot.. certainly never generated graphs in it)
You probably want a stem graph, and then do something like:
stem(event_times, ones(size(event_times));
You can overlay multiple graphs to get the red circles, etc.