how i can import specific rows from excel and than use that row in equations MATLAB .

hI all;

i want to import x rowfrom excel file but those values of x which is greater than 200 not all ,second how i can use this x value in equation like y=3*x+12 in matlab.

Answer 1

[Jon]

You can use the matlab command readmatrix to get the data in from Excel (type doc readmatrix on the command line for details)

This will return all the values in your spreadsheet, not just the ones where x > 200. However if you have now put these into a variable, let's call it x, you can get just those values using something like:

x = x(x>200)

to evaluate the expression you have just use

y = 3*x + 12

Just as you already have it written

[Engineer Batoor khan mummand]

thank u so much from your reply bro ...but The function readmatrix is only available in version 2019 (and later). and i am usin version 2017.

[Engineer Batoor khan mummand]

bro i import data from excel by this matlab code :

clc;
close all;
clear all;
%: Read the excel file using readtable function
x = readtable('bat.xlsx','Sheet','Taxila-hour');
% x = rawTable.day1; 
x = rawTable.solar_radiation; 
plot(x)
ylabel('solar radiation')
title('solar intensity for islamabad condition')

but now i want to take those valuses of x which is greater than 200 not all imported values of x.

second i want to use value of x in this equation.

y = 3*x + 12

thanks

[Jon]

You first read your data into a table called x and then on the next line you assign x to a variable called rawTable.solar_radiation. This second assignment would wipe out the first assignment. Also the variable rawTable.solar_radiation is not defined at the point you assign it to x so this would not work.

I don't know the names of the specific variables (column names) in your table, but generically (you will have to adapt this to how you have things named) you would do something like:

% read the data from the excel sheet into a table
myData = readtable('myFile.xlsx','Sheet','mySheet')

% assign some local variables to make things more readable
% time is in column called 
t = myData.myTimeColumn
x = myData.myValueOfInterestColumn 

% find values that exceed threshold
xThreshold = 200
iKeep = x >= xThreshold

% just keep those values
t = t(iKeep)
x = x(iKeep)

% plot them
plot(t,x)

% calculate some new variable y
y = 3*x + 12

[Engineer Batoor khan mummand]

thank you so much for your reply and your concentration on my problem , let me give you complete information about my problem. i have these below equations and I want to plot(x,s) where x=outlet temperature and s= solar radiation but s is given in excel file name (khan.xlsx )sheet name( sheet1) range from row J2:J1000 and below four equatios are given .

s*x+4y-3z+12m=100
2x+3*s*y+4z+200m=200
3x+y+z+4*s*m=150
25x+20y+10*s*m=250

thank you so much

[Walter Roberson]

Is it certain that x from bat.xlsx is the same size as s from khan.xlsx ?

[Walter Roberson]

You have 4 equations in five variables, two of which are inputs (x and s); and possibly y = 3*x + 12 as well, which would reduce the system to 4 equations in three unknowns. There will not generally be any solution.

[Engineer Batoor khan mummand]

thank you so much from your reply;

i have four unknown and four equations which is given in last comment but s is known which is in excel.

[Engineer Batoor khan mummand]

Dear Walter Roberson :

below four equations and four unknowns (x,y,z,m) but s is given which is in excel khan.xlsx sheet1 and range is J2:J1000.

i want to plot(x,s)

s*x+4y-3z+12m=100

2x+3*s*y+4z+200m=200

3x+y+z+4*s*m=150

25x+20y+10*s*m=250

I want to plot(x,s)

[Walter Roberson]

You indicated earlier that both s and x are read from files.

If you have four equations in four variables, then you can solve the equations to get x, y, z, m based upon s:

          -(50*(15*s^2 + 122*s - 3868))/(- 3*s^3 + 35*s^2 + 568*s + 220)
                     (500*(25*s - 478))/(- 3*s^3 + 35*s^2 + 568*s + 220)
 -(50*(3*s^3 + 70*s^2 - 1464*s + 6164))/(- 3*s^3 + 35*s^2 + 568*s + 220)
           (25*(- 3*s^2 + 110*s + 178))/(- 3*s^3 + 35*s^2 + 568*s + 220)

which you can vectorize.

But this will not use the input x values.

[Engineer Batoor khan mummand]

thanks walter Roberson

;\ i have four equation which is given in last comments and four unknowns but s is given in excell range is J2:J1000.

now i want to plot(x,s)

i need matlab code

thanks u so much

[Engineer Batoor khan mummand]

Dear Walter Roberson :

i want to solve four equations simultaneously in order to find value of x,y,m and z by putting value of s which is given in excel file range J2:J1000 and than plot it against s.

i hope you have got my point