Arduino replace code - gps

Question

I'm very new to Arduino and C programming.
I'm making a GPS speedo and I'm trying to read in some serial, store a value from a substring and echo it back via serial.
At the moment I'm having problems storing the substring.
I've gotten to the point where I'm able to get some data between < and >.
But the data doesn't come in like that. It's a NMEA data stream and the data I want is between ,N, and ,K,.
So I've been trying to replace ,N, with < and ,K, with > .
Just can't get it to work. I get error: request for member 'replace' in 'c', which is of non-class type 'char'
Here's my code so far....
int indata = 0;
int scrubdata = 0;
char inString[32];
int stringPos = 0;
boolean startRead = false; // is reading?
void setup() {
Serial.begin(4800);
}
void loop() {
String pageValue = readPage();
Serial.print(pageValue);
}
String readPage(){
//read the page, and capture & return everything between '<' and '>'
stringPos = 0;
memset( &inString, 0, 32 ); //clear inString memory
while(true){
if (Serial.available() > 0) {
char c = Serial.read();
c.replace(",N,", "<");
c.replace(",K,", ">");
if (c == '<' ) { //'<' is our begining character
startRead = true; //Ready to start reading the part
}
else if(startRead){
if(c != '>'){ //'>' is our ending character
inString[stringPos] = c;
stringPos ++;
}
else{
//got what we need here! We can disconnect now
startRead = false;
return inString;
}
}
}
}
}

Answer 1

By Default:
Serial.read() returns an int if you must process the data this way, try casting it to char with:
char c = (char) Serial.read();
Another way to do this:
Would be to seek your beginning string (discarding un-needed data) using Serial.find() then reading data until you met your end character ",K," with Serial.readBytesUntil()
Something like this would work quite well:
char inData[64]; //adjust for your data size
Serial.setTimeout(2000); //Defaults to 1000 msecs set if necessary
Serial.find(",N,"); //Start of Data
int bRead = Serial.readBytesUntil(",K,", inData, 64); //Read until end of data
inData[bRead] = 0x00; //Zero terminate if using this as a string
return inData;