Read value from a graph

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Marcel Been
Marcel Been 2014-8-26
评论： Marcel Been 2014-8-26
Hello,
I want to read a value from a graph. I´ve got two matrices (X & Y) and plotted in a graph. I want to know the value of Y when i enter the value of X.
PLEASE help me with a code for this problem.
.
CODE:
x=[-879.320000000000;-877.030000000000;-873.430000000000;-869.850000000000;
-866.210000000000;-862.600000000000;-858.900000000000;-857.340000000000;
-855.290000000000;-851.630000000000;-847.980000000000;-844.240000000000;
-840.530000000000;-840.010000000000;-836.820000000000;-833.130000000000;
-829.330000000000;-825.400000000000;-825.400000000000;-821.790000000000;
-818.020000000000;-814.170000000000;-812.670000000000;-810.360000000000;
-806.480000000000;-802.630000000000;-801.150000000000;-798.710000000000;
-794.820000000000;-790.830000000000;-790.620000000000;-786.910000000000;
-782.920000000000;-780.940000000000;-778.930000000000;-774.870000000000;
-771.790000000000;-770.810000000000;-766.750000000000;-763.250000000000;
-762.650000000000];
y =[1;1.09300000000000;1.24200000000000;1.39900000000000;1.56400000000000;
1.73800000000000;1.92000000000000;2;2.11000000000000;2.31000000000000;
2.52000000000000;2.73900000000000;2.96800000000000;3;3.20800000000000;
3.45700000000000;3.71800000000000;3.99000000000000;4;4.27300000000000;
4.56700000000000;4.87400000000000;5;5.19300000000000;5.52400000000000;
5.86800000000000;6;6.22500000000000;6.59500000000000;6.97900000000000;
7;7.37600000000000;7.78830000000000;8;8.21500000000000;8.65600000000000;
9;9.11200000000000;9.58400000000000;10;10.0710000000000];
Total=[matrix1 matrix2];

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回答（1 个）

Ben11
Ben11 2014-8-26
编辑：Ben11 2014-8-26
Not sure to understand how you would like to 'enter' the value of x, but here is a very simple example:
User_x = inputdlg('Enter a value for x'); % Ask the user what value of x he wants
while ~any(ismember(str2double(User_x),x)) % Check if the entered value is indeed in X.
User_x = inputdlg('Enter a value for x');
end
X_index = find(str2double(User_x) == x,1,'first') % Find the index in y
Y_value = y(X_index); % Find the corresponding value
Message = sprintf('The corrsponding y-value is %0.12f \n',Y_value); % Write a message
msgbox(Message) % Display the message
Hope that helps!
  1 个评论
Marcel Been
Marcel Been 2014-8-26
Thanks for your answer, but it isn't what i need. I want to use this command for my simulink simulation. I attached my programm. I want to search for the 'value' of 'Ethalpy Power_1' in the graph (X, Y) and then the Y-value have to appear. So i can use it in my other graph.
If i've got this command, the chart-block will be removed.
Hopefully you (or somebody else) got the answer for this problem.

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