Having trouble finding a row in a table

%I'm trying to load this table and then search for a number within the first column, then load that entire row, I can get it if I use this example: table(5,[1:5]) manually, but cannot get my input to be found and then given to me. I get this error "Operator '==' is not supported for operands of type 'table'." and " Error in e=find(a(:,1)==X);"

load('table.mat');

X=input('What would you like to know?: ');

row=find(table(:,1)==X);

disp('The properties at this temperature are:');

table(row,[1:5])

[VBBV]

You show the error as

 Error in e=find(a(:,1)==X);

but use a different variable name here

row=find(table(:,1)==X);

Any reason why you have different variable names a and table in different places of code? Please show relevant code and /or data

[Image Analyst]

Three people (below) have tried to help you but it seems like we're spinning out wheel because you keep forgetting to attach your table. If you have any more questions, then attach your data and code to read it in with the paperclip icon after you read this:

TUTORIAL: How to ask a question (on Answers) and get a fast answer

Answer 1

[Star Strider]

We do not have ‘a.mat’ to work with.

That aside, it may contain a struct (structure array), and if so, the struct2table function could be a useful initial approach.

You could then use table indexing into the table that function creates.

[Edgar]

Here is the flie, sorry for not thinking of uploading it before.

[Star Strider]

No worries!

Try something like this —

LD = load(websave('a','https://www.mathworks.com/matlabcentral/answers/uploaded_files/1347779/a.mat'))

LD = struct with fields:
    a: [76×5 table]

a = LD.a

a = 76×5 table
    Temperature (C)    Pressure(kPa)    vf (m^3/kg)    vfg (m^3/kg)    vg (m^3/kg)
    _______________    _____________    ___________    ____________    ___________

         0.01             0.6117            0.001            206            206   
            5             0.8725            0.001         147.03         147.03   
           10             1.2281            0.001         106.32         106.32   
           15             1.7057         0.001001         77.884         77.885   
           20             2.3392         0.001002         57.761         57.762   
           25             3.1698         0.001003         43.339          43.34   
           30             4.2469         0.001004         32.878         32.879   
           35             5.6291         0.001006         25.204         25.205   
           40             7.3851         0.001008         16.514         16.515   
           45             9.5953          0.00101          15.25         15.251   
           50             12.352         0.001012         12.025         12.026   
           55             15.763         0.001015         9.5629         9.5639   
           60             19.947         0.001017          7.666          7.667   
           65             25.043          0.00102         6.1925         6.1935   
           70             31.202         0.001023         5.0386         5.0396   
           75             38.597         0.001026         4.1281         4.1291   

VN = a.Properties.VariableNames;
X = 35;
row=find(a.('Temperature (C)')==X)

row = 8

rowinterp = a{row,:};                           % Specific Matching Row
fprintf('The properties at this temperature are: \n%s\t%s\t%s\t%s\t%s\n\t%3d\t%.3f\t\t%.6f\t%.4f\t\t%.4f',VN{:},rowinterp)

The properties at this temperature are: 
Temperature (C)	Pressure(kPa)	vf (m^3/kg)	vfg (m^3/kg)	vg (m^3/kg)
	 35	5.629		0.001006	25.2040		25.2050

T = 42;                                         % Interpolated Values
rowinterp = [T interp1(a{:,1},a{:,2:5},T)];
fprintf('The properties at this temperature are: \n%s\t%s\t%s\t%s\t%s\n\t%3d\t%.3f\t\t%.6f\t%.4f\t\t%.4f',VN{:},rowinterp)

The properties at this temperature are: 
Temperature (C)	Pressure(kPa)	vf (m^3/kg)	vfg (m^3/kg)	vg (m^3/kg)
	 42	8.269		0.001009	16.0084		16.0094

Experiment to get different results.

.

[Edgar]

Thank you so much! I've been struggling for days !

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

.

Answer 2

[Steven Lord]

You need to extract the contents of the table variable if you want to use == on it in the release you're using.

load patients
T = table(LastName, Height, Weight);
firstTenRows = T(1:10, :)

firstTenRows = 10×3 table
      LastName      Height    Weight
    ____________    ______    ______

    {'Smith'   }      71       176  
    {'Johnson' }      69       163  
    {'Williams'}      64       131  
    {'Jones'   }      67       133  
    {'Brown'   }      64       119  
    {'Davis'   }      68       142  
    {'Miller'  }      64       142  
    {'Wilson'  }      68       180  
    {'Moore'   }      68       183  
    {'Taylor'  }      66       132  

Let's find the patients that are 68 inches tall.

patients68 = firstTenRows.Height == 68; % or
patients68 = firstTenRows{:, 'Height'} == 68;
selectedPatients = firstTenRows(patients68, :)

selectedPatients = 3×3 table
     LastName     Height    Weight
    __________    ______    ______

    {'Davis' }      68       142  
    {'Wilson'}      68       180  
    {'Moore' }      68       183  

If you were using release R2023a or later and all the data in your table supported the == operator you could directly perform certain math operations on the table.

justHeightAndWeight = firstTenRows(:, ["Height", "Weight"])

justHeightAndWeight = 10×2 table
    Height    Weight
    ______    ______

      71       176  
      69       163  
      64       131  
      67       133  
      64       119  
      68       142  
      64       142  
      68       180  
      68       183  
      66       132  

justHeightAndWeight(:, "Height") == 68

ans = 10×1 table
    Height
    ______

    false 
    false 
    false 
    false 
    false 
    true  
    false 
    true  
    true  
    false